Ultrasonic Radar Program
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Transcript of Ultrasonic Radar Program
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The project Ultrasonic Distance Radar is a very interesting and useful project for many
project applications. In this project we have used the ultrasonic waves to measure the
distance in between two points. The basic principal is based on the speed of ultrasonic
waves in open air. Sensor’s are mount on the stepper motor bas platform. When circuit is
on then motor moves in one direction and search the object . If the object is located then
sensor provide a feedback and at the same time circuit count the step move by the stepper
motor. By counting the step of stepper motor we show the direction of the object We
have used a microcontroller AT89S51 to transmit and receive ultrasonic waves through
40 KHz ultrasonic receiver and transmitters. By measuring the time required to travel the
unknown distance by ultrasonic waves in air we can find out the distance between two
points. The distance measured is displayed on a LCD display. The transmission &
reception of ultrasonic waves is very complex in nature so it needs very sophisticated
techniques to process these waves. We have used a very complex structure of amplifier
and filters for this purpose. The speed of ultrasonic waves is dependent on temperature.
So before using ultrasonic waves for any measurement we need to calibrate the speed of
ultrasonic waves in current atmospheric temperature. For this purpose we have
implemented a special algorithm to calibrate the speed of ultrasonic waves through a
known distance of 100 Cm.
There are numerous applications of ultrasonic waves in instrumentation and control.
These applications include measurement of distance, speed, flow etc. Ultrasonic also find
many application in medical instrumentation.
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Step DownT/F
Full Wave Bridge
Rectifier
Voltage Regulator
Comparator(sensitivity selector )
Demodulator
Amplifier Circuit 2ndstage
Amplifier Circuit 1st stage
40 KHzUltrasonic Receiver
16x2 LCD Display
40 KHz Ultrasonic Transmitter
Current Amplifier
Driver CircuitMicrocontroller AT89S51
+5VDC/500mA
+9VDC/250mA
230V
AC
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In this project we combine two project. One is ultra sonic distance
measurement and second is direction checker with the . In normal condition
when we press the start switch then stepper motor is rotate. Stepper motor is
connected to the port P1. Pin no 1,2,3,4. Here we use bi-polar stepper motor
to move in the clockwise direction and anticlock wise direction Motor
moves in any direction in steps. It takes a movement is steps. In one step it
moves to 1.8 degree, there is lot of stepper motor available in the market,
Now in these days stepper motor easily available in the market.
In this project we connect the stepper motor to the pin no 1,2,3,4 of the
microcontroller. Here we use 89s51 controller. 89s51 is a 8051 based
controller. In the stepper motor there is four coil. To provide a voltage from
the controller we connect two transistor circuit. Output from the controller is
firstly connected to the base of the PNP transistor via current limiting
resistor. Output from the controller is active low so firstly we provide a
active low output to the base of the PNP transistor and output of the PNP
transistor is connected to the base of the NPN transistor. Emitter of the NPN
transistor connected to the ground pin and collector of the NPN transistor is
connected to the one coil of the stepper motor. Here we use four coil stepper
motor , so we use four series circuit of transistor to to the four coil of the
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Here in this project we use 40 khtz transmitter . This 40 k htz frequency is
generated by the microcontroller. We use one oscillation circuit+ time
circuit to control the sending-out time of the ultrasonic pulse.
The circuit is the same as the ultrasonic range meter .
The oscillation frequency is the same.
The inverter is used for the drive of the ultrasonic sensor. The two inverters
are connected in parallel because of the transmission electric power increase.
The phase with the voltage to apply to the positive terminal and the negative
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terminal of the sensor has been 180 degrees shifted. Because it is cutting the
direct current with the capacitor, about twice of voltage of the inverter
output are appied to the sensor.
The ultrasonic signal which was received with the reception sensor is
amplified by 1000 times(60dB) of voltage with the operational amplifier
with two stages. It is 100 times at the first stage (40dB) and 10 times (20dB)
at the next stage..
Generally, the positive and the negative power supply are used for the
operational amplifier. The circuit this time works with the single power
supply of +9 V. Therefore, for the positive input of the operational
amplifiers, the half of the power supply voltage is applied as the bias voltage
and it is made 4.5 V in the central voltage of the amplified alternating
current signal. When using the operational amplifier with the negative
feedback, the voltage of the positive input terminal and the voltage of the
negative input terminal become equal approximately. So, by this bias
voltage, the side of the positive and the side of the negative of the alternating
current signal can be equally amplified. When not using this bias voltage,
the distortion causes the alternating current signal. When the alternating
current signal is amplified, this way is used when working the operational
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amplifier for the 2 power supply with the single power supply.
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The detection is done to detect the received ultrasonic signal. It is the half-
wave rectification circuit which used the Shottky barrier diodes. The DC
voltage according to the level of the detection signal is gotten by the
capacitor behind the diode. the Shottky barrier diodes are used because the
high frequency characteristic is good.
This circuit is the circuit which detects the ultrasonic which returned from
the object. The output of the detection circuit is detected using the
comparator. At the circuit this time, the operational amplifier of the single
power supply is used instead of the comparator. The operational amplifier
amplifies and outputs the difference between the positive input and the
negative input.
In case of the operational amplifier which doesn't have the negative
feedback, at a little input voltage, the output becomes the saturation state.
Generally, the operational amplifier has tens of thousands of times of mu
factors. So, when the positive input becomes higher a little than the negative
input, the difference is tens of thousands of times amplified and the output
becomes the same as the power supply almost.(It is the saturation state)
Oppositely, when the positive input becomes lower a little than the negative
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input, the difference is tens of thousands of times amplified and the output
becomes 0 V almost.(It is in the OFF condition) This operation is the same
as the operation of the comparator. However, because the inner circuit is
different about the comparator and the operational amplifier, the comparator
can not be used as the
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This circuit is the gate circuit to measure the time which is reflected with the
object and returns after sending out the ultrasonic. It is using the SR (the set
and the reset) flip-flop. For the details of SR-FF, refer to
The set condition is the time which begins to let out the ultrasonic with the
transmitter. It uses the transmission timing pulse.
The reset condition is the time which detected the signal with the signal
detector of the receiver circuit.
That is, the time that the output of SR-FF (D) is in the ON condition
becomes the time which returns after letting out the ultrasonic
The time that the sound wave goes and returns in the 40-cm distanceWhen the ambient temperature is 20°C, the propagation speed of the sound wave is 343.5 m/second.In the time to be propagated by 80 cm (the going and returning), it is as follows.
TS = 0.8/343.5
= 0.00233
= 2.33 milliseconds
The time that the sound wave goes and returns in the 10-m distanceIn the time to be propagated by 20 m (the going and returning), it is as follows.
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TL = 20/343.5
= 0.05822
= 58.2 milliseconds
.
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MICROCONTROLLER AT89C51
Architecture of 8051 family:-
The figure – 1 above shows the basic architecture of 8051 family of microcontroller.
Features• Compatible with MCS-51™ Products
• 4K Bytes of In-System Reprogrammable Flash Memory
– Endurance: 1,000 Write/Erase Cycles
• Fully Static Operation: 0 Hz to 24 MHz
• Three-Level Program Memory Lock
• 128 x 8-Bit Internal RAM
• 32 Programmable I/O Lines
• Two 16-Bit Timer/Counters
• Six Interrupt Sources
• Programmable Serial Channel
• Low Power Idle and Power Down Modes
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Description
The AT89C51 is a low-power, high-performance CMOS 8-bit microcomputer with 4K
bytes of Flash Programmable and Erasable Read Only Memory (PEROM). The device is
manufactured using Atmel’s high density nonvolatile memory technology and is
compatible with the industry standard MCS-51™ instruction set and pinout. The on-chip
Flash allows the program memory to be reprogrammed in-system or by a conventional
nonvolatile memory programmer. By combining a versatile 8-bit CPU with Flash on a
monolithic chip, the Atmel AT89C51 is a powerful microcomputer which provides a
highly flexible and cost effective solution to many embedded control applications. The
AT89C51 provides the following standard features: 4K bytes of Flash, 128 bytes of
RAM, 32 I/O lines, two 16-bit timer/counters, five vector two-level interrupt architecture,
a full duplex serial port, and on-chip oscillator and clock circuitry.
In addition, the AT89C51 is designed with static logic for operation down to zero
frequency and supports two software selectable power saving modes. The Idle Mode
stops the CPU while allowing the RAM, timer/counters, serial port and interrupt system
to continue functioning. The Power down Mode saves the RAM contents but freezes the
oscillator disabling all other chip functions until the next hardware reset.
Pin Description
VCCSupply voltage.
GNDGround.
Port 0Port 0 is an 8-bit open drain bidirectional I/O port. As an output port each pin can sink
eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as high
impedance inputs. Port 0 may also be configured to be the multiplexed low order
address/data bus during accesses to external program and data memory. In this mode P0
has internal pull-ups. Port 0 also receives the code bytes during Flash programming, and
outputs the code bytes during program verification.
External pull-ups are required during program verification.
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Port 1
Port 1 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 1 output buffers
can sink/source four TTL inputs. When 1s are written to Port 1 pins they are pulled high
by the internal pull-ups and can be used as inputs. As inputs, Port 1 pins that are
externally being pulled low will source current (IIL) because of the internal pull-ups. Port
1 also receives the low-order address bytes during Flash programming and verification.
Port 2
Port 2 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 2 output buffers
can sink/source four TTL inputs. When 1s are written to Port 2 pins they are pulled high
by the internal pull-ups and can be used as inputs. As inputs, Port 2 pins that are
externally being pulled low will source current (IIL) because of the internal pull-ups. Port
2 emits the high-order address byte during fetches from external program memory and
during accesses to external data memory that uses 16-bit addresses (MOVX @ DPTR). In
this application it uses strong internal pull-ups when emitting 1s. During accesses to
external data memory that uses 8-bit addresses (MOVX @ RI); Port 2 emits the contents
of the P2 Special Function Register. Port 2 also receives the high-order address bits and
some control signals during Flash programming and verification.
Port 3
Port 3 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 3 output buffers
can sink/source four TTL inputs. When 1s are written to Port 3 pins they are pulled high
by the internal pull-ups and can be used as inputs. As inputs, Port 3 pins that are
externally being pulled low will source current (IIL) because of the pull-ups. Port 3 also
serves the functions of various special features of the AT89C51 as listed below:
Port 3 also receives some control signals for Flash programming and verification.
RST
Reset input. A high on this pin for two machine cycles while the oscillator is running
resets the device.
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ALE/PROG
Address Latch Enable output pulse for latching the low byte of the address during
accesses to external memory. This pin is also the program pulse input (PROG) during
Flash programming. In normal operation ALE is emitted at a constant rate of 1/6 the
oscillator frequency, and may be used for external timing or clocking purposes. Note,
however, that one ALE pulse is skipped during each access to external Data Memory. If
desired, ALE operation can be disabled by setting bit 0 of SFR location 8EH. With the bit
set, ALE is active only during a MOVX or MOVC instruction. Otherwise, the pin is
weakly pulled high. Setting the ALE-disable bit has no effect if the microcontroller is in
external execution mode.
PSEN
Program Store Enable is the read strobe to external program memory.
Port Pin Alternate Functions
P3.0 RXD (serial input port)
P3.1 TXD (serial output port)
P3.2 INT0 (external interrupt 0)
P3.3 INT1 (external interrupt 1)
P3.4 T0 (timer 0 external input)
P3.5 T1 (timer 1 external input)
P3.6 WR (external data memory write strobe)
P3.7 RD (external data memory read strobe)
When the AT89C51 is executing code from external program memory, PSEN is activated
twice each machine cycle, except that two PSEN activations are skipped during each
access to external data memory.
EA/VPP
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External Access Enable. EA must be strapped to GND in order to enable the device to
fetch code from external program memory locations starting at 0000H up to FFFFH.
Note, however, that if lock bit 1 is programmed, EA will be internally latched on reset.
EA should be strapped to VCC for internal program executions. This pin also receives the
12-volt programming enable voltage (VPP) during Flash programming, for parts that
require 12-volt VPP.
XTAL1
Input to the inverting oscillator amplifier and input to the internal clock operating circuit.
XTAL2
Output from the inverting oscillator amplifier.
Oscillator Characteristics
XTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier
which can be configured for use as an on-chip oscillator, as shown in Figure 1. Either a
quartz crystal or ceramic resonator may be used. To drive the device from an external
clock source, XTAL2 should be left unconnected while XTAL1 is driven as shown in
Figure 2.There are no requirements on the duty cycle of the external clock signal, since
the input to the internal clocking circuitry is through a divide-by-two flip-flop, but
minimum and maximum voltage high and low time specifications must be observed.
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Idle Mode
In idle mode, the CPU puts itself to sleep while all the on chip peripherals remain active.
The mode is invoked by software. The content of the on-chip RAM and all the special
functions registers remain unchanged during this mode. The idle mode can be terminated
by any enabled
Interrupt or by hardware reset. It should be noted that when idle is terminated by a hard
Hardware reset, the device normally resumes program execution, from where it left off,
up to two machine cycles before the internal reset algorithm takes control. On-chip
hardware inhibits access to internal RAM in this event, but access to the port pins is not
inhibited. To eliminate the possibility of an unexpected write to a port pin when Idle is
terminated by reset, the instruction following the one that invokes Idle should not be one
that writes to a port pin or to external memory.
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Status of External Pins during Idle and Power down Modes
Mode Program Memory ALE PSEN PORT0 PORT1 PORT2 PORT3
Idle Internal 1 Data
Idle External 1 Float Data Address Data
Power down Internal 0 Data
Power down External 0 Float Data
Power down Mode
In the power down mode the oscillator is stopped, and the instruction that invokes power
down is the last instruction executed. The on-chip RAM and Special Function Registers
retain their values until the power down mode is terminated. The only exit from power
down is a hardware reset. Reset redefines the SFRs but does not change the on-chip
RAM. The reset should not be activated before VCC is restored to its normal operating
level and must be held active long enough to allow the oscillator to restart and stabilize.
Program Memory Lock Bits
On the chip are three lock bits which can be left un-programmed (U) or can be
programmed (P) to obtain the additional features listed in the table below:
When lock bit 1 is programmed, the logic level at the EA pin is sampled and latched
during reset. If the device is powered up without a reset, the latch initializes to a random
value, and holds that value until reset is activated. It is necessary that the latched value of
EA be in agreement with
The current logic level at that pin in order for the device to function properly.
Lock Bit Protection Modes
Program Lock Bits Protection Type
LB1 LB2 LB3
1 U No program lock features.
2 P U MOVC instructions executed from external program memory are disabled from
fetching code
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Bytes from internal memory, EA is sampled and latched on reset, and further
programming of the
Flash is disabled.
3 P U Same as mode 2, also verify is disabled.
4 P same as mode 3, also external execution is disabled.
Programming the Flash
The AT89C51 is normally shipped with the on-chip Flash memory array in the erased
state (that is, contents = FFH) and ready to be programmed. The programming interface
accepts either a high-voltage (12-volt) or a low-voltage (VCC) program enable signal.
The low voltage programming mode provides a convenient way to program the AT89C51
inside the user’s system, while the high-voltage programming mode is compatible with
conventional third party Flash or EPROM programmers. The AT89C51 is shipped with
either the high-voltage or low-voltage programming mode enabled. The respective top-
side marking and device signature codes are listed in the following table. The AT89C51
code memory array is programmed byte-by byte
In either programming mode. To program any nonblank byte in the on-chip Flash
Memory, the entire memory must be erased using the Chip Erase Mode.
Programming Algorithm:
Before programming the AT89C51, the address, data and control signals should be set up
according to the Flash programming mode table and Figures 3 and 4. To program the
AT89C51, take the following steps.
1. Input the desired memory location on the address lines.
2. Input the appropriate data byte on the data lines.
3. Activate the correct combination of control signals.
4. Raise EA/VPP to 12V for the high-voltage programming mode.
5. Pulse ALE/PROG once to program a byte in the Flash array or the lock bits. The byte-
write cycle is self-timed and typically takes no more than 1.5 ms. Repeat steps 1 through
5, changing the address and data for the entire array or until the end of the object file is
reached.
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Data Polling:
The AT89C51 features Data Polling to indicate the end of a write cycle. During a write
cycle, an attempted read of the last byte written will result in the complement of the
written datum on PO.7. Once the write cycle has been completed, true data are valid on
all outputs, and the next cycle may begin. Data Polling may begin any time after a write
cycle has been initiated.
Ready/Busy:
The progress of byte programming can also be monitored by the RDY/BSY output
signal. P3.4 is pulled low after ALE goes high during programming to indicate BUSY.
P3.4 is pulled high again when programming is done to indicate READY.
Program Verify:
If lock bits LB1 and LB2 have not been programmed, the programmed code data can be
read back via the address and data lines for verification. The lock bits cannot be verified
directly. Verification of the lock bits is achieved by observing that their features are
enabled.
Chip Erase:
The entire Flash array is erased electrically by using the proper combination of control
signals and by holding ALE/PROG low for 10 ms. The code array is written with all
“1”s. The chip erase operation must be executed before the code memory can be re-
programmed.
Reading the Signature Bytes:
The signature bytes are read by the same procedure as a normal verification of locations
030H,
031H, and 032H, except that P3.6 and P3.7 must be pulled to a logic low. The values
returned are as follows.
(030H) = 1EH indicates manufactured by Atmel
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(031H) = 51H indicates 89C51
(032H) = FFH indicates 12V programming
(032H) = 05H indicates 5V programming
Programming Interface
Every code byte in the Flash array can be written and the entire array can be erased by
using the appropriate combination of control signals. The write operation cycle is self
timed and once initiated, will automatically time itself to completion. All major
programming vendors offer worldwide support for the Atmel microcontroller series.
Please contact your local programming vendor for the appropriate software revision.
Flash Programming Modes
Note: 1. Chip Erase requires a 10-ms PROG pulse.
SPECIAL FUNCTION REGISTER (SFR) ADDRESSES:
ACC ACCUMULATOR 0E0H
B B REGISTER 0F0H
PSW PROGRAM STATUS WORD 0D0H
SP STACK POINTER 81H
DPTR DATA POINTER 2 BYTES
DPL LOW BYTE OF DPTR 82H
DPH HIGH BYTE OF DPTR 83H
P0 PORT0 80H
P1 PORT1 90H
P2 PORT2 0A0H
P3 PORT3 0B0H
TMOD TIMER/COUNTER MODE CONTROL 89H
TCON TIMER COUNTER CONTROL 88H
TH0 TIMER 0 HIGH BYTE 8CH
TLO TIMER 0 LOW BYTE 8AH
TH1 TIMER 1 HIGH BYTE 8DH
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TL1 TIMER 1 LOW BYTE 8BH
SCON SERIAL CONTROL 98H
SBUF SERIAL DATA BUFFER 99H
PCON POWER CONTROL 87H
TMOD (TIMER MODE) REGISTER
Both timers are the 89c51 share the one register TMOD. 4 LSB bit for the timer 0 and 4
MSB for the timer 1.
In each case lower 2 bits set the mode of the timer
Upper two bits set the operations.
GATE: Gating control when set. Timer/counter is enabled only while the INTX
pin is high and the TRx control pin is set. When cleared, the timer is enabled whenever
the TRx control bit is set
C/T: Timer or counter selected cleared for timer operation (input from internal
system clock)
M1 Mode bit 1
M0 Mode bit 0
M1 M0 MODE OPERATING MODE
0 0 0 13 BIT TIMER/MODE
0 1 1 16 BIT TIMER MODE
1 0 2 8 BIT AUTO RELOAD
1 1 3 SPLIT TIMER MODE
PSW (PROGRAM STATUS WORD)
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CY PSW.7 CARRY FLAG
AC PSW.6 AUXILIARY CARRY
F0 PSW.5 AVAILABLE FOR THE USER FRO GENERAL PURPOSE
RS1 PSW.4 REGISTER BANK SELECTOR BIT 1
RS0 PSW.3 REGISTER BANK SELECTOR BIT 0
0V PSW.2 OVERFLOW FLAG
-- PSW.1 USER DEFINABLE BIT
P PSW.0 PARITY FLAG SET/CLEARED BY HARDWARE
PCON REGISATER (NON BIT ADDRESSABLE)
If the SMOD = 0 (DEFAULT ON RESET)
TH1 = CRYSTAL FREQUENCY
256---- ____________________
384 X BAUD RATE
If the SMOD IS = 1
CRYSTAL FREQUENCY
TH1 = 256--------------------------------------
192 X BAUD RATE
There are two ways to increase the baud rate of data transfer in the 8051
1. To use a higher frequency crystal
2. To change a bit in the PCON register
PCON register is an 8 bit register. Of the 8 bits, some are unused, and some are used for
the power control capability of the 8051. The bit which is used for the serial
communication is D7, the SMOD bit. When the 8051 is powered up, D7 (SMOD BIT)
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OF PCON register is zero. We can set it to high by software and thereby double the baud
rate
BAUD RATE COMPARISION FOR SMOD = 0 AND SMOD =1
TH1 (DECIMAL) HEX SMOD =0 SMOD =1
-3 FD 9600 19200
-6 FA 4800 9600
-12 F4 2400 4800
-24 E8 1200 2400
XTAL = 11.0592 MHZ
IE (INTERRUPT ENABLE REGISTOR)
EA IE.7 Disable all interrupts if EA = 0, no interrupts is acknowledged
If EA is 1, each interrupt source is individually enabled or disabled
By sending or clearing its enable bit.
IE.6 NOT implemented
ET2 IE.5 enables or disables timer 2 overflag in 89c52 only
ES IE.4 Enables or disables all serial interrupt
ET1 IE.3 Enables or Disables timer 1 overflow interrupt
EX1 IE.2 Enables or disables external interrupt
ET0 IE.1 Enables or Disables timer 0 interrupt.
EX0 IE.0 Enables or Disables external interrupt 0
INTERRUPT PRIORITY REGISTER
If the bit is 0, the corresponding interrupt has a lower priority and if the bit is 1 the
corresponding interrupt has a higher priority
IP.7 NOT IMPLEMENTED, RESERVED FOR FUTURE USE.
IP.6 NOT IMPLEMENTED, RESERVED FOR FUTURE USE
PT2 IP.5 DEFINE THE TIMER 2 INTERRUPT PRIORITY LELVEL
PS IP.4 DEFINES THE SERIAL PORT INTERRUPT PRIORITY LEVEL
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PT1 IP.3 DEFINES THE TIMER 1 INTERRUPT PRIORITY LEVEL
PX1 IP.2 DEFINES EXTERNAL INTERRUPT 1 PRIORITY LEVEL
PT0 IP.1 DEFINES THE TIMER 0 INTERRUPT PRIORITY LEVEL
PX0 IP.0 DEFINES THE EXTERNAL INTERRUPT 0 PRIORITY LEVEL
SCON: SERIAL PORT CONTROL REGISTER, BIT ADDRESSABLE
SCON
SM0 : SCON.7 Serial Port mode specified
SM1 : SCON.6 Serial Port mode specifier
SM2 : SCON.5
REN : SCON.4 Set/cleared by the software to Enable/disable reception
TB8 : SCON.3 the 9th bit that will be transmitted in modes 2 and 3, Set/cleared
By software
RB8 : SCON.2 In modes 2 &3, is the 9th data bit that was received. In mode 1,
If SM2 = 0, RB8 is the stop bit that was received. In mode 0
RB8 is not used
T1 : SCON.1 Transmit interrupt flag. Set by hardware at the end of the 8th bit
Time in mode 0, or at the beginning of the stop bit in the other
Modes. Must be cleared by software
R1 SCON.0 Receive interrupt flag. Set by hardware at the end of the 8th bit
Time in mode 0, or halfway through the stop bit time in the other
Modes. Must be cleared by the software.
TCON TIMER COUNTER CONTROL REGISTER
This is a bit addressable
TF1 TCON.7 Timer 1 overflows flag. Set by hardware when the Timer/Counter
1
Overflows. Cleared by hardware as processor
TR1 TCON.6 Timer 1 run control bit. Set/cleared by software to turn Timer
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Counter 1 On/off
TF0 TCON.5 Timer 0 overflows flag. Set by hardware when the timer/counter 0
Overflows. Cleared by hardware as processor
TR0 TCON.4 Timer 0 run control bit. Set/cleared by software to turn timer
Counter 0 on/off.
IE1 TCON.3 External interrupt 1 edge flag
ITI TCON.2 Interrupt 1 type control bit
IE0 TCON.1 External interrupt 0 edge
IT0 TCON.0 Interrupt 0 type control bit.
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MCS-51 FAMILY INSTRUCTION SET
Notes on Data Addressing Modes
Rn - Working register R0-R7
Direct - 128 internal RAM locations, any l/O port, control or status register
@Ri - Indirect internal or external RAM location addressed by register R0 or R1
#data - 8-bit constant included in instruction
#data 16 - 16-bit constant included as bytes 2 and 3 of instruction
Bit - 128 software flags, any bit addressable l/O pin, control or status bit
A - Accumulator
Notes on Program Addressing Modes
addr16 - Destination address for LCALL and LJMP may be anywhere within the 64-
Kbyte program memory address space. addr11 - Destination address for ACALL and
AJMP will be within the same 2-Kbyte page of program memory as the first byte of the
following instruction. Rel - SJMP and all conditional jumps include an 8 bit offset byte.
Range is + 127/– 128 bytes relative to the first byte of the following instruction.
ACALL addr11
Function: Absolute call
Description: ACALL unconditionally calls a subroutine located at the indicated address.
The instruction increments the PC twice to obtain the address of the following
instruction, then pushes the 16-bit result onto the stack (low-order byte first) and
increments the stack pointer twice. The destination address is obtained by successively
concatenating the five high-order bits of the incremented PC, op code bits 7-5, and the
second byte of the instruction. The subroutine called must therefore start within the same
2K block of program memory as the first byte of the instruction following ACALL. No
flags are affected. Example: Initially SP equals 07H. The label”SUBRTN” is at program
memory location 0345H. After executing the instruction ACALL SUBRTN at location
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0123H, SP will contain 09H, internal RAM location 08H and 09H will contain 25H and
01H, respectively, and the PC will contain 0345H.
Operation: ACALL
(PC) ¬ (PC) + 2
(SP) ¬ (SP) + 1
((SP)) ¬ (PC7-0)
(SP) ¬ (SP) + 1
((SP)) ¬ (PC15-8)
(PC10-0) ¬ Page address
Bytes: 2
Cycles: 2
Encoding: a10 a9 a8 1 0 0 0 1 a7 a6 a5 a4 a3 a2 a1 a0
ADD A, <src-byte>
Function: Add
Description: ADD adds the byte variable indicated to the accumulator, leaving the result
in the accumulator. The carry and auxiliary carry flags are set, respectively, if there is a
Carry out of bit 7 or bit 3, and cleared otherwise. When adding unsigned integers, the
carry flag indicates an overflow occurred. OV is set if there is a carry out of bit 6 but not
out of bit 7, or a carry out of bit 7 but not out of bit 6; otherwise OV is cleared. When
adding signed integers, OV indicates a negative number produced as the sum of two
positive operands, or a positive sum from two negative operands. Four source operand
addressing modes are allowed: register, direct, register indirect, or immediate.
Example: The accumulator holds 0C3H (11000011B) and register 0 holds 0AAH
(10101010B). The instruction ADD A, R0 will leave 6DH (01101101B) in the
accumulator with the AC flag cleared and both the carry flag and OV set to 1.
ADD A,Rn
Operation: ADD
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(A) ¬ (A) + (Rn)
Bytes: 1
Cycles: 1
ADD A, direct
Operation: ADD
(A) ¬ (A) + (direct)
Bytes: 2
Cycles: 1
Encoding: 0 0 1 0 1 r r r
Encoding: 0 0 1 0 0 1 0 1 direct address
ADD A, @Ri
Operation: ADD
(A) ¬ (A) + ((Ri))
Bytes: 1
Cycles: 1
ADD A, #data
Operation: ADD
(A) ¬ (A) + #data
Bytes: 2
Cycles: 1
Encoding: 0 0 1 0 0 1 1 i
Encoding: 0 0 1 0 0 1 0 0 immediate data
ADDC A, < src-byte>
Function: Add with carry
Description: ADDC simultaneously adds the byte variable indicated, the carry flag and
the accumulator contents, leaving the result in the accumulator. The carry and auxiliary
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Carry flags are set, respectively, if there is a carry out of bit 7 or bit 3, and cleared
otherwise. When adding unsigned integers, the carry flag indicates an overflow occurred.
OV is set if there is a carry out of bit 6 but not out of bit 7, or a carry out of bit 7 but not
out of bit 6; otherwise OV is cleared. When adding signed integers, OV indicates a
negative number produced as the sum of two positive operands or a positive sum from
two negative operands. Four source operand addressing modes are allowed: register,
direct, register indirect, or immediate.
Example: The accumulator holds 0C3H (11000011B) and register 0 holds 0AAH
(10101010B) with the carry flag set. The instruction ADDC A, R0 will leave 6EH
(01101110B) in the accumulator with AC cleared and both the carry flag and OV set to 1.
ADDC A, Rn
Operation: ADDC
(A) ¬ (A) + (C) + (Rn)
Bytes: 1
Cycles: 1
ADDC A, direct
Operation: ADDC
(A) ¬ (A) + (C) + (direct)
Bytes: 2
Cycles: 1
Encoding: 0 0 1 1 1 r r r
Encoding: 0 0 1 1 0 1 0 1 direct address
ADDC A, @Ri
Operation: ADDC
(A) ¬ (A) + (C) + ((Ri))
Bytes: 1
Cycles: 1
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ADDC A, #data
Operation: ADDC
(A) ¬ (A) + (C) + #data
Bytes: 2
Cycles: 1
Encoding: 0 0 1 1 0 1 1 i
Encoding: 0 0 1 1 0 1 0 0 immediate data
AJMP addr11
Function: Absolute jump
Description: AJMP transfers program execution to the indicated address, which is formed
at runtime by concatenating the high-order five bits of the PC (after incrementing the PC
twice), op code bits 7-5, and the second byte of the instruction. The destination must
therefore be within the same 2K block of program memory as the first byte of the
instruction following AJMP.
Example: The label”JMPADR” is at program memory location 0123H. The instruction
AJMP JMPADR is at location 0345H and will load the PC with 0123H.
Operation: AJM P
(PC) ¬ (PC) + 2
(PC10-0) ¬ Page address
Bytes: 2
Cycles: 2
Encoding: a10 a9 a8 0 0 0 0 1 a7 a6 a5 a4 a3 a2 a1 a0
ANL <dest-byte>, <src-byte>
Function: Logical AND for byte variables
Description: ANL performs the bitwise logical AND operation between the variables
indicated and stores the results in the destination variable. No flags are affected. The two
operands allow six addressing mode combinations. When the destination is an
accumulator, the source can use register, direct, register-indirect, or immediate
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addressing; when the destination is a direct address, the source can be the accumulator or
immediate data.
Note:
When this instruction is used to modify an output port, the value used as the original
Port data will be read from the output data latch, not the input pins.
Example: If the accumulator holds 0C3H (11000011B) and register 0 holds 0AAH
(10101010B) then the instruction
ANL A, R0
Will leave 81H (10000001B) in the accumulator.
When the destination is a directly addressed byte, this instruction will clear combinations
of bits in any RAM location or hardware register. The mask byte determining the pattern
of bits to be cleared would either be a constant contained in the instruction or a value
computed in the accumulator at run-time.
The instruction ANL P1, #01110011B will clear bits 7, 3, and 2 of output port 1.
ANL A, Rn
Operation: ANL
(A) ¬ (A) Ù (Rn)
Bytes: 1
Cycles: 1
Encoding: 0 1 0 1 1 r r r
ANL A, direct
Operation: ANL
(A) ¬ (A) Ù (direct)
Bytes: 2
Cycles: 1
ANL A, @Ri
Operation: ANL
(A) ¬ (A) Ù ((Ri))
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Bytes: 1
Cycles: 1
ANL A, #data
Operation: ANL
(A) ¬ (A) Ù #data
Bytes: 2
Cycles: 1
ANL direct, A
Operation: ANL
(direct) ¬ (direct) Ù (A)
Bytes: 2
Cycles: 1
Encoding: 0 1 0 1 0 1 0 1 direct address
Encoding: 0 1 0 1 0 1 1 i
Encoding: 0 1 0 1 0 1 0 0 immediate data
Encoding: 0 1 0 1 0 1 0 1 direct address
ANL direct, #data
Operation: ANL
(direct) ¬ (direct) Ù #data
Bytes: 3
Cycles: 2
Encoding: 0 1 0 1 0 0 1 1 direct address immediate data
ANL C, <src-bit>
Function: Logical AND for bit variables
Description: If the Boolean value of the source bit is logic 0 then clear the carry flag;
otherwise leave the carry flag in its current state. A slash (”/” preceding the operand in
the assembly language indicates that the logical complement of the addressed bit is used
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as the source value, but the source bit itself is not affected. No other flags are affected.
Only direct bit addressing is allowed for the source operand.
Example: Set the carry flag if and only if, P1.0 = 1, ACC.7 = 1 and OV = 0:
MOV C, P1.0; Load carry with input pin state
ANL C, ACC.7; AND carry with accumulator bit 7
ANL C, /OV; AND with inverse of overflow flag
ANL C, bit
Operation: ANL
(C) ¬ (C) Ù (bit)
Bytes: 2
Cycles: 2
ANL C, /bit
Operation: ANL
(C) ¬ (C) Ù Ø (bit)
Bytes: 2
Cycles: 2
Encoding: 1 0 0 0 0 0 1 0 bit address
Encoding: 1 0 1 1 0 0 0 0 bit address
CJNE <dest-byte >, < src-byte >, rel
Function: Compare and jump if not equal
Description: CJNE compares the magnitudes of the first two operands, and branches if
their values are not equal. The branch destination is computed by adding the signed
relative displacement in the last instruction byte to the PC, after incrementing the PC to
the start of the next instruction. The carry flag is set if the unsigned integer value of
<dest-byte> is less than the unsigned integer value of <src-byte>; otherwise, the carry is
cleared. Neither operand is affected. The first two operands allow four addressing mode
combinations: the accumulator may be compared with any directly addressed byte or
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immediate data, and any indirect RAM location or working register can be compared
with an immediate constant.
Example: The accumulator contains 34H. Register 7 contains 56H. The first instruction in
the sequence CJNE R7, # 60H, NOT_EQ; . . . . . . . . ; R7 = 60H NOT_EQ JC
REQ_LOW; If R7 < 60H; . . . . . . . . ; R7 > 60H sets the carry flag and branches to the
instruction at label NOT_EQ. By testing the carry flag, this instruction determines
whether R7 is greater or less than 60H. If the data being presented to port 1 is also 34H,
then the instruction WAIT: CJNE A, P1, WAIT clears the carry flag and continues with
the next instruction in sequence, since the accumulator does equal the data read from P1.
(If some other value was input on P1, the program will loop at this point until the P1 data
changes to 34H).
CJNE A, direct, rel
Operation: (PC) ¬ (PC) + 3
if (A) < > (direct)
then (PC) ¬ (PC) + relative offset
if (A) < (direct)
then (C) ¬1
else (C) ¬ 0
Bytes: 3
Cycles: 2
CJNE A, #data, rel
Operation: (PC) ¬ (PC) + 3
if (A) < > data
then (PC) ¬ (PC) + relative offset
if (A) ¬ data
then (C) ¬1
else (C) ¬ 0
Bytes: 3
Cycles: 2
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CJNE RN, #data, rel
Operation: (PC) ¬ (PC) + 3
if (Rn) < > data
then (PC) ¬ (PC) + relative offset
if (Rn) < data
then (C) ¬ 1
else (C) ¬ 0
Bytes: 3
Cycles: 2
Encoding: 1 0 1 1 0 1 0 1 direct address rel. address
Encoding: 1 0 1 1 0 1 0 0 immediate data rel. address
Encoding: 1 0 1 1 1 r r r immediate data rel. address
CJNE @Ri, #data, rel
Operation: (PC) ¬ (PC) + 3
if ((Ri)) < > data
then (PC) ¬ (PC) + relative offset
if ((Ri)) < data
then (C) ¬ 1
else (C) ¬ 0
Bytes: 3
Cycles: 2
Encoding: 1 0 1 1 0 1 1 i immediate data rel. address
CLR A
Function: Clear accumulator
Description: The accumulator is cleared (all bits set to zero). No flags are affected.
Example: The accumulator contains 5CH (01011100B). The instruction
CLR A
will leave the accumulator set to 00H (00000000B).
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Operation: CLR
(A) ¬ 0
Bytes: 1
Cycles: 1
Encoding: 1 1 1 0 0 1 0 0
CLR bit
Function: Clear bit
Description: The indicated bit is cleared (reset to zero). No other flags are affected. CLR
can operate on the carry flag or any directly addressable bit. Example: Port 1 has
previously been written with 5DH (01011101B). The instruction
CLR P1.2
will leave the port set to 59H (01011001B).
CLR C
Operation: CLR
(C) ¬ 0
Bytes: 1
Cycles: 1
CLR bit
Operation: CLR
(bit) ¬ 0
Bytes: 2
Cycles: 1
Encoding: 1 1 0 0 0 0 1 1
Encoding: 1 1 0 0 0 0 1 0 bit address
CPL A
Function: Complement accumulator
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Description: Each bit of the accumulator is logically complemented (one’s complement).
Bits which previously contained a one are changed to zero and vice versa. No flags are
affected.
Example: The accumulator contains 5CH (01011100B). The instruction
CPL A
will leave the accumulator set to 0A3H (10100011 B).
Operation: CPL
(A) ¬ Ø (A)
Bytes: 1
Cycles: 1
Encoding: 1 1 1 1 0 1 0 0
CPL bit
Function: Complement bit
Description: The bit variable specified is complemented. A bit which had been a one is
changed to zero and vice versa. No other flags are affected. CPL can operate on the carry
or any directly addressable bit.
Note:
When this instruction is used to modify an output pin, the value used as the original data
will be read from the output data latch, not the input pin.
Example: Port 1 has previously been written with 5DH (01011101B). The instruction
sequence
CPL P1.1
CPL P1.2
will leave the port set to 5BH (01011011B).
CPL C
Operation: CPL
(C) ¬ Ø (C)
Bytes: 1
Cycles: 1
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CPL bit
Operation: CPL
(bit) ¬ Ø (bit)
Bytes: 2
Cycles: 1
Encoding: 1 0 1 1 0 0 1 1
Encoding: 1 0 1 1 0 0 1 0 bit address
DA A
Function: Decimal adjust accumulator for addition
Description: DA A adjusts the eight-bit value in the accumulator resulting from the
earlier addition of two variables (each in packed BCD format), producing two four-bit
digits. Any ADD or ADDC instruction may have been used to perform the addition.
If accumulator bits 3-0 are greater than nine (xxxx1010-xxxx1111), or if the AC flag
is one, six is added to the accumulator producing the proper BCD digit in the low order
nibble. This internal addition would set the carry flag if a carry-out of the low order
four-bit field propagated through all high-order bits, but it would not clear the carry flag
otherwise.
If the carry flag is now set, or if the four high-order bits now exceed nine (1010xxxx-
1111xxxx), these high-order bits are incremented by six, producing the proper BCD digit
in the high-order nibble. Again, this would set the carry flag if there was a carryout of the
high-order bits, but wouldn’t clear the carry. The carry flag thus indicates if the sum of
the original two BCD variables is greater than 100, allowing multiple precision decimal
additions. OV is not affected.
All of this occurs during the one instruction cycle. Essentially; this instruction performs
the decimal conversion by adding 00H, 06H, 60H, or 66H to the accumulator, depending
on initial accumulator and PSW conditions.
Note:
DA A cannot simply convert a hexadecimal number in the accumulator to BCD notation,
nor does DA A apply to decimal subtraction.
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Example: The accumulator holds the value 56H (01010110B) representing the packed
BCD digits of the decimal number 56. Register 3 contains the value 67H (01100111B)
representing the packed BCD digits of the decimal number 67. The carry flag is set.
The instruction sequence
ADDC A, R3
DA A
will first perform a standard two’s-complement binary addition, resulting in the value
0BEH (10111110B) in the accumulator. The carry and auxiliary carry flags will be
cleared.
The decimal adjust instruction will then alter the accumulator to the value 24H
(00100100B), indicating the packed BCD digits of the decimal number 24, the low order
two digits of the decimal sum of 56, 67, and the carry-in. The carry flag will be set by the
decimal adjust instruction, indicating that a decimal overflow occurred.
The true sum 56, 67, and 1 is 124.
BCD variables can be incremented or decremented by adding 01H or 99H. If the
accumulator initially holds 30H (representing the digits of 30 decimal), then the
instruction sequence
ADD A, #99H
DA A
will leave the carry set and 29H in the accumulator, since 30 + 99 = 129. The low order
byte of the sum can be interpreted to mean 30 – 1 = 29.
Operation: DA
contents of accumulator are BCD
if [[(A3-0) > 9] Ú [(AC) = 1]]
then (A3-0) ¬ (A3-0) + 6
and
if [[(A7-4) > 9] Ú [(C) = 1]]
then (A7-4) ¬ (A7-4) + 6
Bytes: 1
Cycles: 1
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Encoding: 1 1 0 1 0 1 0 0
DEC byte
Function: Decrement
Description: The variable indicated is decremented by 1. An original value of 00H wills
underflow to 0FFH. No flags are affected. Four operand addressing modes are allowed:
accumulator, register, direct, or register-indirect.
Note:
When this instruction is used to modify an output port, the value used as the original
port data will be read from the output data latch, not the input pins.
Example: Register 0 contains 7FH (01111111B). Internal RAM locations 7EH and 7FH
contain 00H and 40H, respectively. The instruction sequence
DEC @R0
DEC R0
DEC @R0
will leave register 0 set to 7EH and internal RAM locations 7EH and 7FH set to 0FFH
and 3FH.
DEC A
Operation: DEC
(A) ¬ (A) – 1
Bytes: 1
Cycles: 1
DEC Rn
Operation: DEC
(Rn) ¬ (Rn) – 1
Bytes: 1
Cycles: 1
Encoding: 0 0 0 1 0 1 0 0
Encoding: 0 0 0 1 1 r r r
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DEC direct
Operation: DEC
(direct) ¬ (direct) – 1
Bytes: 2
Cycles: 1
DEC @Ri
Operation: DEC
((Ri)) ¬ ((Ri)) – 1
Bytes: 1
Cycles: 1
Encoding: 0 0 0 1 0 1 0 1 direct address
Encoding: 0 0 0 1 0 1 1 i
DIV AB
Function: Divide
Description: DIV AB divides the unsigned eight-bit integer in the accumulator by the
unsigned eight-bit integer in register B. The accumulator receives the integer part of the
quotient; register B receives the integer remainder. The carry and OV flags will be
cleared.
Exception: If B had originally contained 00H, the values returned in the accumulator and
B register will be undefined and the overflow flag will be set. The carry flag is cleared in
any case.
Example: The accumulator contains 251 (0FBH or 11111011B) and B contains 18 (12H
or
00010010B). The instruction
DIV AB
will leave 13 in the accumulator (0DH or 00001101 B) and the value 17 (11H or
00010001B) in B, since 251 = (13x18) + 17. Carry and OV will both be cleared.
Operation: DIV
(A15-8)
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(B7-0)
Bytes: 1
Cycles: 4
Encoding: 1 0 0 0 0 1 0 0
¬ (A) / (B)
DJNZ <byte>, < rel-addr>
Function: Decrement and jump if not zero
Description: DJNZ decrements the location indicated by 1, and branches to the address
indicated by the second operand if the resulting value is not zero. An original value of
00H wills underflow to 0FFH. No flags are affected. The branch destination would be
computed by adding the signed relative-displacement value in the last instruction byte to
the PC, after incrementing the PC to the first byte of the following instruction. The
location decremented may be a register or directly addressed byte.
Note:
When this instruction is used to modify an output port, the value used as the original port
data will be read from the output data latch, not the input pins.
Example: Internal RAM locations 40H, 50H, and 60H contain the values, 01H, 70H, and
15H, respectively. The instruction sequence
DJNZ 40H, LABEL_1
DJNZ 50H, LABEL_2
DJNZ 60H, LABEL_3
will cause a jump to the instruction at label LABEL_2 with the values 00H, 6FH, and
15H in the three RAM locations. The first jump was not taken because the result was
zero.
This instruction provides a simple way of executing a program loop a given number of
times, or for adding a moderate time delay (from 2 to 512 machine cycles) with a single
instruction. The instruction sequence
MOV R2, #8
TOGGLE: CPL P1.7
DJNZ R2, TOGGLE
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will toggle P1.7 eight times, causing four output pulses to appear at bit 7 of output port 1.
Each pulse will last three machine cycles; two for DJNZ and one to alter the pin.
DJNZ Rn, rel
Operation: DJNZ
(PC) ¬ (PC) + 2
(Rn) ¬ (Rn) – 1
if (Rn) > 0 or (Rn) < 0
then (PC) ¬ (PC) + rel
Bytes: 2
Cycles: 2
DJNZ direct, rel
Operation: DJNZ
(PC) ¬ (PC) + 2
(direct) ¬ (direct) – 1
if (direct) > 0 or (direct) < 0
then (PC) ¬ (PC) + rel
Bytes: 3
Cycles: 2
Encoding: 1 1 0 1 1 r r r rel. address
Encoding: 1 1 0 1 0 1 0 1 direct address rel. address
INC <byte>
Function: Increment
Description: INC increments the indicated variable by 1. An original value of 0FFH will
overflow to 00H. No flags are affected. Three addressing modes are allowed: register,
direct, or register-indirect.
Note:
When this instruction is used to modify an output port, the value used as the original
port data will be read from the output data latch, not the input pins.
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Example: Register 0 contains 7EH (01111110B). Internal RAM locations 7EH and 7FH
contain 0FFH and 40H, respectively. The instruction sequence
INC @R0
INC R0
INC @R0
will leave register 0 set to 7FH and internal RAM locations 7EH and 7FH holding
(respectively) 00H and 41H.
INC A
Operation: INC
(A) ¬ (A) + 1
Bytes: 1
Cycles: 1
INC Rn
Operation: INC
(Rn) ¬ (Rn) + 1
Bytes: 1
Cycles: 1
Encoding: 0 0 0 0 0 1 0 0
Encoding: 0 0 0 0 1 r r r
INC direct
Operation: INC
(direct) ¬ (direct) + 1
Bytes: 2
Cycles: 1
INC @Ri
Operation: INC
((Ri)) ¬ ((Ri)) + 1
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Bytes: 1
Cycles: 1
Encoding: 0 0 0 0 0 1 0 1 direct address
Encoding: 0 0 0 0 0 1 1 i
INC DPTR
Function: Increment data pointer
Description: Increment the 16-bit data pointer by 1. A 16-bit increment (modulo 216) is
performed; an overflow of the low-order byte of the data pointer (DPL) from 0FFH to
00H will increment the high-order byte (DPH). No flags are affected. This is the only 16-
bit register which can be incremented.
Example: Registers DPH and DPL contain 12H and 0FEH, respectively. The instruction
sequence
INC DPTR
INC DPTR
INC DPTR
will change DPH and DPL to 13H and 01H.
Operation: INC
(DPTR) ¬ (DPTR) + 1
Bytes: 1
Cycles: 2
Encoding: 1 0 1 0 0 0 1 1
JB bit, rel
Function: Jump if bit is set
Description: If the indicated bit is a one, jump to the address indicated; otherwise proceed
with the next instruction. The branch destination is computed by adding the signed
relative-displacement in the third instruction byte to the PC, after incrementing the PC to
the first byte of the next instruction. The bit tested is not modified. No flags are affected.
Example: The data present at input port 1 is 11001010B. The accumulator holds 56
(01010110B). The instruction sequence
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JB P1.2, LABEL1
JB ACC.2, LABEL2
will cause program execution to branch to the instruction at label LABEL2.
Operation: JB
(PC) ¬ (PC) + 3
if (bit) = 1
then (PC) ¬ (PC) + rel
Bytes: 3
Cycles: 2
Encoding: 0 0 1 0 0 0 0 0 bit address rel. address
JBC bit, rel
Function: Jump if bit is set and clear bit
Description: If the indicated bit is one, branch to the address indicated; otherwise proceed
with the next instruction. In either case, clear the designated bit. The branch destination is
computed by adding the signed relative displacement in the third instruction byte to the
PC, after incrementing the PC to the first byte of the next instruction. No flags are
affected.
Note:
When this instruction is used to test an output pin, the value used as the original data will
be read from the output data latch, not the input pin.
Example: The accumulator holds 56H (01010110B). The instruction sequence
JBC ACC.3, LABEL1
JBC ACC.2, LABEL2
will cause program execution to continue at the instruction identified by the label
LABEL2, with the accumulator modified to 52H (01010010B).
Operation: JBC
(PC) ¬ (PC) + 3
if (bit) = 1
then (bit) ¬ 0
(PC) ¬ (PC) + rel
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Bytes: 3
Cycles: 2
Encoding: 0 0 0 1 0 0 0 0 bit address rel. address
JC rel
Function: Jump if carry is set
Description: If the carry flag is set, branch to the address indicated; otherwise proceed
with the next instruction. The branch destination is computed by adding the signed
relative displacement in the second instruction byte to the PC, after incrementing the PC
twice. No flags are affected.
Example: The carry flag is cleared. The instruction sequence
JC LABEL1
CPL C
JC LABEL2
will set the carry and cause program execution to continue at the instruction identified by
the label LABEL2.
Operation: JC
(PC) ¬ (PC) + 2
if (C) = 1
then (PC) ¬ (PC) + rel
Bytes: 2
Cycles: 2
Encoding: 0 1 0 0 0 0 0 0 rel. address
JMP @A + DPTR
Function: Jump indirect
Description: Add the eight-bit unsigned contents of the accumulator with the sixteen-bit
data pointer, and load the resulting sum to the program counter. This will be the address
for subsequent instruction fetches. Sixteen-bit addition is performed (modulo 216): a
carry-out from the low-order eight bits propagates through the higher-order bits. Neither
the accumulator nor the data pointer is altered. No flags are affected.
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Example: An even number from 0 to 6 is in the accumulator. The following sequence of
instructions will branch to one of four AJMP instructions in a jump table starting at
JMP_TBL:
MOV DPTR, #JMP_TBL
JMP @A + DPTR
JMP_TBL: AJMP LABEL0
AJMP LABEL1
AJMP LABEL2
AJMP LABEL3
If the accumulator equals 04H when starting this sequence, execution will jump to label
LABEL2. Remember that AJMP is a two-byte instruction, so the jump instructions start
at every other address.
Operation: JMP
(PC) ¬ (A) + (DPTR)
Bytes: 1
Cycles: 2
Encoding: 0 1 1 1 0 0 1 1
JNB bit, rel
Function: Jump if bit is not set
Description: If the indicated bit is a zero, branch to the indicated address; otherwise
proceed with the next instruction. The branch destination is computed by adding the
signed relative-displacement in the third instruction byte to the PC, after incrementing the
PC to the first byte of the next instruction. The bit tested is not modified. No flags are
affected.
Example: The data present at input port 1 is 11001010B. The accumulator holds 56H
(01010110B). The instruction sequence
JNB P1.3, LABEL1
JNB ACC.3, LABEL2
will cause program execution to continue at the instruction at label LABEL2.
Operation: JNB
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(PC) ¬ (PC) + 3
if (bit) = 0
then (PC) ¬ (PC) + rel.
Bytes: 3
Cycles: 2
Encoding: 0 0 1 1 0 0 0 0 bit address rel. address
JNC rel
Function: Jump if carry is not set
Description: If the carry flag is a zero, branch to the address indicated; otherwise proceed
with the next instruction. The branch destination is computed by adding the signed
relative-displacement in the second instruction byte to the PC, after incrementing the PC
twice to point to the next instruction. The carry flag is not modified.
Example: The carry flag is set. The instruction sequence
JNC LABEL1
CPL C
JNC LABEL2
will clear the carry and cause program execution to continue at the instruction identified
by the label LABEL2.
Operation: JNC
(PC) ¬ (PC) + 2
if (C) = 0
then (PC) ¬ (PC) + rel
Bytes: 2
Cycles: 2
Encoding: 0 1 0 1 0 0 0 0 rel. address
JNZ rel
Function: Jump if accumulator is not zero
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Description: If any bit of the accumulator is a one, branch to the indicated address;
otherwise proceed with the next instruction. The branch destination is computed by
adding the signed relative-displacement in the second instruction byte to the PC, after
incrementing the PC twice. The accumulator is not modified. No flags are affected.
Example: The accumulator originally holds 00H. The instruction sequence
JNZ LABEL1
INC A
JNZ LABEL2
will set the accumulator to 01H and continue at label LABEL2.
Operation: JNZ
(PC) ¬ (PC) + 2
if (A) ¹ 0
then (PC) ¬ (PC) + rel.
Bytes: 2
Cycles: 2
Encoding: 0 1 1 1 0 0 0 0 rel. address
JZ rel
Function: Jump if accumulator is zero
Description: If all bits of the accumulator are zero, branch to the address indicated;
otherwise proceed with the next instruction. The branch destination is computed by
adding the signed relative-displacement in the second instruction byte to the PC, after
incrementing the PC twice. The accumulator is not modified. No flags are affected.
Example: The accumulator originally contains 01H. The instruction sequence
JZ LABEL1
DEC A
JZ LABEL2
will change the accumulator to 00H and cause program execution to continue at the
instruction identified by the label LABEL2.
Operation: JZ
(PC) ¬ (PC) + 2
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if (A) = 0
then (PC) ¬ (PC) + rel
Bytes: 2
Cycles: 2
Encoding: 0 1 1 0 0 0 0 0 rel. address
LCALL addr16
Function: Long call
Description: LCALL calls a subroutine located at the indicated address. The instruction
adds three to the program counter to generate the address of the next instruction and then
pushes the 16-bit result onto the stack (low byte first), incrementing the stack pointer by
two. The high-order and low-order bytes of the PC are then loaded, respectively, with the
second and third bytes of the LCALL instruction. Program execution continues with the
instruction at this address. The subroutine may therefore begin anywhere in the full 64
Kbytes program memory address space. No flags are affected.
Example: Initially the stack pointer equals 07H. The label”SUBRTN” is assigned to
program memory location 1234H. After executing the instruction
LCALL SUBRTN
at location 0123H, the stack pointer will contain 09H, internal RAM locations 08H and
09H will contain 26H and 01H, and the PC will contain 1234H.
Operation: LCALL
(PC) ¬ (PC) + 3
(SP) ¬ (SP) + 1
((SP)) ¬ (PC7-0)
(SP) ¬ (SP) + 1
((SP)) ¬ (PC15-8)
(PC) ¬ addr15-0
Bytes: 3
Cycles: 2
Encoding: 0 0 0 1 0 0 1 0 addr15. . addr8 addr7. . addr0
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LJMP addr16
Function: Long jump
Description: LJMP causes an unconditional branch to the indicated address, by loading
the high order and low-order bytes of the PC (respectively) with the second and third
instruction bytes. The destination may therefore be anywhere in the full 64K program
memory address space. No flags are affected.
Example: The label”JMPADR” is assigned to the instruction at program memory location
1234H. The instruction
LJMP JMPADR
at location 0123H will load the program counter with 1234H.
Operation: LJMP
(PC) ¬ addr15-0
Bytes: 3
Cycles: 2
Encoding: 0 0 0 0 0 0 1 0 addr15 . . . addr8 addr7 . . . addr0
MOV <dest-byte>, <src-byte>
Function: Move byte variable
Description: The byte variable indicated by the second operand is copied into the location
specified by the first operand. The source byte is not affected. No other register or flag is
affected. This is by far the most flexible operation. Fifteen combinations of source and
destination addressing modes are allowed.
Example: Internal RAM location 30H holds 40H. The value of RAM location 40H is
10H. The data present at input port 1 is 11001010B (0CAH).
MOV R0, #30H; R0 < = 30H
MOV A, @R0; A < = 40H
MOV R1, A; R1 < = 40H
MOV B, @R1; B < = 10H
MOV @R1, P1; RAM (40H) < = 0CAH
MOV P2, P1; P2 < = 0CAH
leaves the value 30H in register 0, 40H in both the accumulator and register 1, 10H
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in register B, and 0CAH (11001010B) both in RAM location 40H and output on port 2.
MOV A, Rn
Operation: MOV
(A) ¬ (Rn)
Bytes: 1
Cycles: 1
MOV A, direct *)
Operation: MOV
(A) ¬ (direct)
Bytes: 2
Cycles: 1
*) MOV A, ACC is not a valid instruction.
Encoding: 1 1 1 0 1 r r r
Encoding: 1 1 1 0 0 1 0 1 direct address
MOV A,@Ri
Operation: MOV
(A) ¬ ((Ri))
Bytes: 1
Cycles: 1
MOV A, #data
Operation: MOV
(A) ¬ #data
Bytes: 2
Cycles: 1
MOV Rn, A
Operation: MOV
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(Rn) ¬ (A)
Bytes: 1
Cycles: 1
MOV Rn, direct
Operation: MOV
(Rn) ¬ (direct)
Bytes: 2
Cycles: 2
Encoding: 1 1 1 0 0 1 1 i
Encoding: 0 1 1 1 0 1 0 0 immediate data
Encoding: 1 1 1 1 1 r r r
Encoding: 1 0 1 0 1 r r r direct address
MOV Rn, #data
Operation: MOV
(Rn) ¬ #data
Bytes: 2
Cycles: 1
MOV direct, A
Operation: MOV
(direct) ¬ (A)
Bytes: 2
Cycles: 1
MOV direct, Rn
Operation: MOV
(direct) ¬ (Rn)
Bytes: 2
Cycles: 2
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MOV direct, direct
Operation: MOV
(direct) ¬ (direct)
Bytes: 3
Cycles: 2
Encoding: 0 1 1 1 1 r r r immediate data
Encoding: 1 1 1 1 0 1 0 1 direct address
Encoding: 1 0 0 0 1 r r r direct address
Encoding: 1 0 0 0 0 1 0 1 dir.addr. (src) dir.addr. (dest)
MOV direct, @ Ri
Operation: MOV
(direct) ¬ ((Ri))
Bytes: 2
Cycles: 2
MOV direct, #data
Operation: MOV
(direct) ¬ #data
Bytes: 3
Cycles: 2
MOV @ Ri, A
Operation: MOV
((Ri)) ¬ (A)
Bytes: 1
Cycles: 1
MOV @ Ri, direct
Operation: MOV
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((Ri)) ¬ (direct)
Bytes: 2
Cycles: 2
Encoding: 1 0 0 0 0 1 1 i direct address
Encoding: 0 1 1 1 0 1 0 1 direct address immediate data
Encoding: 1 1 1 1 0 1 1 i
Encoding: 1 0 1 0 0 1 1 i direct address
MOV @ Ri, #data
Operation: MOV
((Ri)) ¬ #data
Bytes: 2
Cycles: 1
Encoding: 0 1 1 1 0 1 1 i immediate data
MOV <dest-bit>, <src-bit>
Function: Move bit data
Description: The Boolean variable indicated by the second operand is copied into the
location specified by the first operand. One of the operands must be the carry flag; the
other may be any directly addressable bit. No other register or flag is affected.
Example: The carry flag is originally set. The data present at input port 3 is 11000101B.
The data previously written to output port 1 is 35H (00110101B).
MOV P1.3, C
MOV C, P3.3
MOV P1.2, C
will leave the carry cleared and change port 1 to 39H (00111001 B).
MOV C, bit
Operation: MOV
(C) ¬ (bit)
Bytes: 2
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Cycles: 1
MOV bit, C
Operation: MOV
(bit) ¬ (C)
Bytes: 2
Cycles: 2
Encoding: 1 0 1 0 0 0 1 0 bit address
Encoding: 1 0 0 1 0 0 1 0 bit address
MOV DPTR, #data16
Function: Load data pointer with a 16-bit constant
Description: The data pointer is loaded with the 16-bit constant indicated. The 16 bit
constant is loaded into the second and third bytes of the instruction. The second byte
(DPH) is the high-order byte, while the third byte (DPL) holds the low-order byte. No
flags are affected. This is the only instruction which moves 16 bits of data at once.
Example: The instruction
MOV DPTR, #1234H
will load the value 1234H into the data pointer: DPH will hold 12H and DPL will hold
34H.
Operation: MOV
(DPTR) ¬ #data15-0
DPH DPL ¬ #data15-8 #data7-0
Bytes: 3
Cycles: 2
Encoding: 1 0 0 1 0 0 0 0 immed. data 15 . . . 8 immed. data 7 . . . 0
MOVC A, @A + <base-reg>
Function: Move code byte
Description: The MOVC instructions load the accumulator with a code byte, or constant
from program memory. The address of the byte fetched is the sum of the original
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unsigned eight-bit accumulator contents and the contents of a sixteen-bit base register,
which may be either the data pointer or the PC. In the latter case, the PC is incremented
to the address of the following instruction before being added to the accumulator;
otherwise the base register is not altered. Sixteen-bit addition is performed so a carry-out
from the low-order eight bits may propagate through higher-order bits. No flags are
affected.
Example: A value between 0 and 3 is in the accumulator. The following instructions will
translate the value in the accumulator to one of four values defined by the DB (define
byte) directive.
REL_PC: INC A
MOVC A, @A + PC
RET
DB 66H
DB 77H
DB 88H
DB 99H
If the subroutine is called with the accumulator equal to 01H, it will return with 77H in
the accumulator. The INC A before the MOVC instruction is needed to”get around” the
RET instruction above the table. If several bytes of code separated the MOVC from the
table, the corresponding number would be added to the accumulator instead.
MOVC A, @A + DPTR
Operation: MOVC
(A) ¬ ((A) + (DPTR))
Bytes: 1
Cycles: 2
Encoding: 1 0 0 1 0 0 1 1
MOVC A, @A + PC
Operation: MOVC
(PC) ¬ (PC) + 1
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(A) ¬ ((A) + (PC))
Bytes: 1
Cycles: 2
Encoding: 1 0 0 0 0 0 1 1
MOVX <dest-byte>, <src-byte>
Function: Move external
Description: The MOVX instructions transfer data between the accumulator and a byte of
external data memory, hence the”X” appended to MOV. There are two types of
instructions, differing in whether they provide an eight bit or sixteen-bit indirect address
to the external data RAM. In the first type, the contents of R0 or R1 in the current register
bank provide an eight-bit address multiplexed with data on P0. Eight bits are sufficient
for external l/O expansion decoding or a relatively small RAM array. For somewhat
larger arrays, any output port pins can be used to output higher-order address bits. These
pins would be controlled by an output instruction preceding the MOVX. In the second
type of MOVX instructions, the data pointer generates a sixteen-bit address. P2 outputs
the high-order eight address bits (the contents of DPH) while P0 multiplexes the low-
order eight bits (DPL) with data. The P2 special function register retains its previous
contents while the P2 output buffers are emitting the contents of DPH. This form is faster
and more efficient when accessing very large data arrays (up to 64 Kbytes), since no
additional instructions are needed to set up the output ports. It is possible in some
situations to mix the two MOVX types. A large RAM array with its high-order address
lines driven by P2 can be addressed via the data pointer, or with code to output high-
order address bits to P2 followed by a MOVX instruction using R0 or R1.
Example: An external 256 byte RAM using multiplexed address/data lines (e.g. an SAB
8155 RAM/I/O/timer) is connected to the SAB 80(c) 5XX port 0. Port 3 provides control
lines for the external RAM. Ports 1 and 2 are used for normal l/O. Registers 0 and 1
contain 12H and 34H. Location 34H of the external RAM holds the value 56H. The
instruction sequence
MOVX A, @R1
MOVX @R0, A
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copies the value 56H into both the accumulator and external RAM location 12H.
MOVX A,@Ri
Operation: MOVX
(A) ¬ ((Ri))
Bytes: 1
Cycles: 2
MOVX A,@DPTR
Operation: MOVX
(A) ¬ ((DPTR))
Bytes: 1
Cycles: 2
MOVX @Ri, A
Operation: MOVX
((Ri)) ¬ (A)
Bytes: 1
Cycles: 2
MOVX @DPTR, A
Operation: MOVX
((DPTR)) ¬ (A)
Bytes: 1
Cycles: 2
Encoding: 1 1 1 0 0 0 1 i
Encoding: 1 1 1 0 0 0 0 0
Encoding: 1 1 1 1 0 0 1 i
Encoding: 1 1 1 1 0 0 0 0
MUL AB
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Function: Multiply
Description: MUL AB multiplies the unsigned eight-bit integers in the accumulator and
register B. The low-order byte of the sixteen-bit product is left in the accumulator, and
the high-order byte in B. If the product is greater than 255 (0FFH) the overflow flag is
set; otherwise it is cleared. The carry flag is always cleared. Example: Originally the
accumulator holds the value 80 (50H). Register B holds the value 160 (0A0H). The
instruction
MUL AB
will give the product 12,800 (3200H), so B is changed to 32H (00110010B) and the
accumulator is cleared. The overflow flag is set, carry is cleared.
Operation: MUL
(A7-0)
(B15-8)
Bytes: 1
Cycles: 4
Encoding: 1 0 1 0 0 1 0 0
¬ (A) x (B)
NOP
Function: No operation
Description: Execution continues at the following instruction. Other than the PC, no
registers or flags are affected.
Example: It is desired to produce a low-going output pulse on bit 7 of port 2 lasting
exactly 5 cycles. A simple SETB/CLR sequence would generate a one-cycle pulse, so
four additional cycles must be inserted. This may be done (assuming no interrupts are
enabled) with the instruction sequence
CLR P2.7
NOP
NOP
NOP
NOP
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SETB P2.7
Operation: NOP
Bytes: 1
Cycles: 1
Encoding: 0 0 0 0 0 0 0 0
ORL <dest-byte> <src-byte>
Function: Logical OR for byte variables
Description: ORL performs the bitwise logical OR operation between the indicated
variables, storing the results in the destination byte. No flags are affected. The two
operands allow six addressing mode combinations. When the destination is the
accumulator, the source can use register, direct, register-indirect, or immediate
addressing; when the destination is a direct address, the source can be the accumulator or
immediate data.
Note:
When this instruction is used to modify an output port, the value used as the original port
data will be read from the output data latch, not the input pins.
Example: If the accumulator holds 0C3H (11000011B) and R0 holds 55H (01010101B)
then the instruction
ORL A, R0
will leave the accumulator holding the value 0D7H (11010111B).
When the destination is a directly addressed byte, the instruction can set combinations of
bits in any RAM location or hardware register. The pattern of bits to be set is determined
by a mask byte, which may be either a constant data value in the instruction or a variable
computed in the accumulator at run-time. The instruction
ORL P1, #00110010B
will set bits 5, 4, and 1 of output port 1.
ORL A, Rn
Operation: ORL
(A) ¬ (A) Ú (Rn)
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Bytes: 1
Cycles: 1
Encoding: 0 1 0 0 1 r r r
ORL A, direct
Operation: ORL
(A) ¬ (A) Ú (direct)
Bytes: 2
Cycles: 1
ORL A,@Ri
Operation: ORL
(A) ¬ (A) Ú ((Ri))
Bytes: 1
Cycles: 1
ORL A, data
Operation: ORL
(A) ¬ (A) Ú #data
Bytes: 2
Cycles: 1
ORL direct, A
Operation: ORL
(direct) ¬ (direct) Ú (A)
Bytes: 2
Cycles: 1
Encoding: 0 1 0 0 0 1 0 1 direct address
Encoding: 0 1 0 0 0 1 1 i
Encoding: 0 1 0 0 0 1 0 0 immediate data
Encoding: 0 1 0 0 0 0 1 0 direct address
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ORL direct, #data
Operation: ORL
(direct) ¬ (direct) Ú #data
Bytes: 3
Cycles: 2
Encoding: 0 1 0 0 0 0 1 1 direct address immediate data
ORL C, <src-bit>
Function: Logical OR for bit variables
Description: Set the carry flag if the Boolean value is logic 1; leave the carry in its
current state otherwise. A slash (”/”) preceding the operand in the assembly language
indicates that the logical complement of the addressed bit is used as the source value, but
the source bit itself is not affected. No other flags are affected.
Example: Set the carry flag if and only if, P1.0 = 1, ACC.7 = 1 or OV = 0:
MOV C, P1.0; Load carry with input pin P1.0
ORL C, ACC.7; OR carry with the accumulator bit 7
ORL C, /OV; OR carry with the inverse of OV
ORL C, bit
Operation: ORL
(C) ¬ (C) Ú (bit)
Bytes: 2
Cycles: 2
ORL C, /bit
Operation: ORL
(C) ¬ (C) Ú Ø (bit)
Bytes: 2
Cycles: 2
Encoding: 0 1 1 1 0 0 1 0 bit address
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Encoding: 1 0 1 0 0 0 0 0 bit address
POP direct
Function: Pop from stack
Description: The contents of the internal RAM location addressed by the stack pointer are
read, and the stack pointer is decremented by one. The value read is the transfer to the
directly addressed byte indicated. No flags are affected.
Example: The stack pointer originally contains the value 32H, and internal RAM
locations 30H
through 32H contain the values 20H, 23H, and 01H, respectively. The instruction
sequence
POP DPH
POP DPL
will leave the stack pointer equal to the value 30H and the data pointer set to 0123H.
At this point the instruction
POP SP
will leave the stack pointer set to 20H. Note that in this special case the stack pointer
was decremented to 2FH before being loaded with the value popped (20H).
Operation: POP
(direct) ¬ ((SP))
(SP) ¬ (SP) – 1
Bytes: 2
Cycles: 2
Encoding: 1 1 0 1 0 0 0 0 direct address
PUSH direct
Function: Push onto stack
Description: The stack pointer is incremented by one. The contents of the indicated
variable is then copied into the internal RAM location addressed by the stack pointer.
Otherwise no flags are affected.
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Example: On entering an interrupt routine the stack pointer contains 09H. The data
pointer holds the value 0123H. The instruction sequence
PUSH DPL
PUSH DPH
will leave the stack pointer set to 0BH and store 23H and 01H in internal RAM locations
0AH and 0BH, respectively.
Operation: PUSH
(SP) ¬ (SP) + 1
((SP)) ¬ (direct)
Bytes: 2
Cycles: 2
Encoding: 1 1 0 0 0 0 0 0 direct address
RET
Function: Return from subroutine
Description: RET pops the high and low-order bytes of the PC successively from the
stack, decrementing the stack pointer by two. Program execution continues at the
resulting address, generally the instruction immediately following an ACALL or LCALL.
No flags are affected.
Example: The stack pointer originally contains the value 0BH. Internal RAM locations
0AH and 0BH contain the values 23H and 01H, respectively. The instruction RET will
leave the stack pointer equal to the value 09H. Program execution will continue at
location 0123H.
Operation: RET
(PC15-8) ¬ ((SP))
(SP) ¬ (SP) – 1
(PC7-0) ¬ ((SP))
(SP) ¬ (SP) – 1
Bytes: 1
Cycles: 2
Encoding: 0 0 1 0 0 0 1 0
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RETI
Function: Return from interrupt
Description: RETI pops the high and low-order bytes of the PC successively from the
stack, and restores the interrupt logic to accept additional interrupts at the same priority
level as the one just processed. The stack pointer is left decremented by two. No other
registers are affected; the PSW is not automatically restored to its pre-interrupt status.
Program execution continues at the resulting address, which is generally the instruction
immediately after the point at which the interrupt request was detected. If a lower or
same-level interrupt is pending when the RETI instruction is executed, that one
instruction will be executed before the pending interrupt is processed.
Example: The stack pointer originally contains the value 0BH. An interrupt was detected
during the instruction ending at location 0122H. Internal RAM locations 0AH and 0BH
contain the values 23H and 01H, respectively. The instruction
RETI
will leave the stack pointer equal to 09H and return program execution to location
0123H.
Operation: RETI
(PC15-8) ¬ ((SP))
(SP) ¬ (SP) – 1
(PC7-0) ¬ ((SP))
(SP) ¬ (SP) – 1
Bytes: 1
Cycles: 2
Encoding: 0 0 1 1 0 0 1 0
RL A
Function: Rotate accumulator left
Description: The eight bits in the accumulator are rotated one bit to the left. Bit 7 is
rotated into the bit 0 position. No flags are affected.
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Example: The accumulator holds the value 0C5H (11000101B). The instruction RL A
leaves the accumulator holding the value 8BH (10001011B) with the carry unaffected.
Operation: RL
(An + 1) ¬ (An) n = 0-6
(A0) ¬ (A7)
Bytes: 1
Cycles: 1
Encoding: 0 0 1 0 0 0 1 1
RLC A
Function: Rotate accumulator left through carry flag
Description: The eight bits in the accumulator and the carry flag are together rotated one
bit to the left. Bit 7 moves into the carry flag; the original state of the carry flag moves
into the bit 0 position. No other flags are affected.
Example: The accumulator holds the value 0C5H (11000101B), and the carry is zero.
The instruction
RLC A
leaves the accumulator holding the value 8AH (10001010B) with the carry set.
Operation: RLC
(An + 1) ¬ (An) n = 0-6
(A0) ¬ (C)
(C) ¬ (A7)
Bytes: 1
Cycles: 1
Encoding: 0 0 1 1 0 0 1 1
RR A
Function: Rotate accumulator right
Description: The eight bits in the accumulator are rotated one bit to the right. Bit 0 is
rotated into the bit 7 positions. No flags are affected.
Example: The accumulator holds the value 0C5H (11000101B). The instruction
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RR A
leaves the accumulator holding the value 0E2H (11100010B) with the carry unaffected.
Operation: RR
(An) ¬ (An + 1) n = 0-6
(A7) ¬ (A0)
Bytes: 1
Cycles: 1
Encoding: 0 0 0 0 0 0 1 1
RRC A
Function: Rotate accumulator right through carry flag
Description: The eight bits in the accumulator and the carry flag are together rotated one
bit to the right. Bit 0 moves into the carry flag; the original value of the carry flag moves
into the bit 7 position. No other flags are affected.
Example: The accumulator holds the value 0C5H (11000101B), the carry is zero. The
instruction
RRC A
leaves the accumulator holding the value 62H (01100010B) with the carry set.
Operation: RRC
(An) ¬ (An + 1) n=0-6
(A7) ¬ (C)
(C) ¬ (A0)
Bytes: 1
Cycles: 1
Encoding: 0 0 0 1 0 0 1 1
SETB <bit>
Function: Set bit
Description: SETB sets the indicated bit to one. SETB can operate on the carry flag or
any directly addressable bit. No other flags are affected.
Example: The carry flag is cleared. Output port 1 has been written with the value 34H
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(00110100B). The instructions
SETB C
SETB P1.0
will leave the carry flag set to 1 and change the data output on port 1 to 35H
(00110101B).
SETB C
Operation: SETB
(C) ¬ 1
Bytes: 1
Cycles: 1
SETB bit
Operation: SETB
(bit) ¬ 1
Bytes: 2
Cycles: 1
Encoding: 1 1 0 1 0 0 1 1
Encoding: 1 1 0 1 0 0 1 0 bit address
SJMP rel
Function: Short jump
Description: Program control branches unconditionally to the address indicated. The
branch destination is computed by adding the signed displacement in the second
instruction byte to the PC, after incrementing the PC twice. Therefore, the range of
destinations allowed is from 128 bytes preceding this instruction to 127 bytes following
it.
Example: The label ”RELADR” is assigned to an instruction at program memory location
0123H. The instruction
SJMP RELADR
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will assemble into location 0100H. After the instruction is executed, the PC will contain
the value 0123H.
Note:
Under the above conditions the instruction following SJMP will be at 102H. Therefore,
the displacement byte of the instruction will be the relative offset (0123H-0102H) = 21H.
In other words, an SJMP with a displacement of 0FEH would be a one-instruction infinite
loop.
Operation: SJMP
(PC) ¬ (PC) + 2
(PC) ¬ (PC) + rel
Bytes: 2
Cycles: 2
Encoding: 1 0 0 0 0 0 0 0 rel. address
SUBB A, <src-byte>
Function: Subtract with borrow
Description: SUBB subtracts the indicated variable and the carry flag together from the
accumulator, leaving the result in the accumulator. SUBB sets the carry (borrow) flag if a
borrow is needed for bit 7, and clears C otherwise. (If C was set before executing a
SUBB instruction, this indicates that a borrow was needed for the previous step in a
multiple precision subtraction, so the carry is subtracted from the accumulator along with
the source operand). AC is set if a borrow is needed for bit 3, and cleared otherwise. OV
is set if a borrow is needed into bit 6 but not into bit 7, or into bit 7 but not bit 6. When
subtracting signed integers OV indicates a negative number produced when a negative
value is subtracted from a positive value or a positive result when a positive number is
subtracted from a negative number. The source operand allows four addressing modes:
register, direct, register indirect, or immediate.
Example: The accumulator holds 0C9H (11001001B), register 2 holds 54H (01010100B),
and the carry flag is set. The instruction
SUBB A, R2
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will leave the value 74H (01110100B) in the accumulator, with the carry flag and AC
cleared but OV set. Notice that 0C9H minus 54H is 75H. The difference between this and
the above result is due to the (borrow) flag being set before the operation. If the state of
the carry is not known before starting a single or multiple-precision subtraction, it should
be explicitly cleared by a CLR C instruction.
SUBB A, Rn
Operation: SUBB
(A) ¬ (A) – (C) – (Rn)
Bytes: 1
Cycles: 1
SUBB A, direct
Operation: SUBB
(A) ¬ (A) – (C) – (direct)
Bytes: 2
Cycles: 1
SUBB A, @ Ri
Operation: SUBB
(A) ¬ (A) – (C) – ((Ri))
Bytes: 1
Cycles: 1
SUBB A, #data
Operation: SUBB
(A) ¬ (A) – (C) – #data
Bytes: 2
Cycles: 1
Encoding: 1 0 0 1 0 1 0 1 direct address
Encoding: 1 0 0 1 0 1 1 i
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Encoding: 1 0 0 1 0 1 0 0 immediate data
SWAP A
Function: Swap nibbles within the accumulator
Description: SWAP A interchanges the low and high-order nibbles (four-bit fields) of the
accumulator (bits 3-0 and bits 7-4). The operation can also be thought of as a four bit
rotate instruction. No flags are affected.
Example: The accumulator holds the value 0C5H (11000101B). The instruction
SWAP A
leaves the accumulator holding the value 5CH (01011100B).
Operation: SWAP
(A3-0) (A7-4), (A7-4) ¬ (A3-0)
Bytes: 1
Cycles: 1
Encoding: 1 1 0 0 0 1 0 0
XCH A, <byte>
Function: Exchange accumulator with byte variable
Description: XCH loads the accumulator with the contents of the indicated variable, at
the same time writing the original accumulator contents to the indicated variable. The
source/destination operand can use register, direct, or register-indirect addressing.
Example: R0 contains the address 20H. The accumulator holds the value 3FH
(00111111B).
Internal RAM location 20H holds the value 75H (01110101B). The instruction
XCH A, @R0
will leave RAM location 20H holding the value 3FH (00111111 B) and 75H
(01110101B) in the accumulator.
XCH A, Rn
Operation: XCH
(A) (Rn)
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Bytes: 1
Cycles: 1
XCH A, direct
Operation: XCH
(A) (direct)
Bytes: 2
Cycles: 1
Encoding: 1 1 0 0 1 r r r
Encoding: 1 1 0 0 0 1 0 1 direct address
XCH A, @ Ri
Operation: XCH
(A) ((Ri))
Bytes: 1
Cycles: 1
Encoding: 1 1 0 0 0 1 1 i
XCHD A,@Ri
Function: Exchange digit
Description: XCHD exchanges the low-order nibble of the accumulator (bits 3-0,
generally representing a hexadecimal or BCD digit); with that of the internal RAM
location indirectly addressed by the specified register. The high-order nibbles (bits 7-4)
of each register are not affected. No flags are affected.
Example: R0 contains the address 20H. The accumulator holds the value 36H
(00110110B). Internal RAM location 20H holds the value 75H (01110101B). The
instruction
XCHD A, @ R0
will leave RAM location 20H holding the value 76H (01110110B) and 35H (00110101B)
in the accumulator.
Operation: XCHD
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(A3-0) ((Ri) 3-0)
Bytes: 1
Cycles: 1
Encoding: 1 1 0 1 0 1 1 i
XRL <dest-byte>, <src-byte>
Function: Logical Exclusive OR for byte variables
Description: XRL performs the bitwise logical Exclusive OR operation between the
indicated variables, storing the results in the destination. No flags are affected. The two
operands allow six addressing mode combinations. When the destination is the
accumulator, the source can use register, direct, register-indirect, or immediate
addressing; when the destination is a direct address, the source can be accumulator or
immediate data.
Note:
When this instruction is used to modify an output port, the value used as the original
port data will be read from the output data latch, not the input pins.
Example: If the accumulator holds 0C3H (11000011B) and register 0 holds 0AAH
(10101010B) then the instruction
XRL A, R0
will leave the accumulator holding the value 69H (01101001B).
When the destination is a directly addressed byte, this instruction can complement
combinations of bits in any RAM location or hardware register. The pattern of bits to be
complemented is then determined by a mask byte, either a constant contained in the
instruction or a variable computed in the accumulator at run-time. The instruction
XRL P1, #00110001B
will complement bits 5, 4, and 0 of output port 1.
XRL A, Rn
Operation: XRL2
(A) ¬ (A) ^ (Rn)
Bytes: 1
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Cycles: 1
Encoding: 0 1 1 0 1 r r r
XRL A, direct
Operation: XRL
(A) ¬ (A) ^ (direct)
Bytes: 2
Cycles: 1
XRL A, @ Ri
Operation: XRL
(A) ¬ (A) ^ ((Ri))
Bytes: 1
Cycles: 1
XRL A, #data
Operation: XRL
(A) ¬ (A) #data
Bytes: 2
Cycles: 1
XRL direct, A
Operation: XRL
(direct) ¬ (direct) ^ (A)
Bytes: 2
Cycles: 1
Encoding: 0 1 1 0 0 1 0 1 direct address
Encoding: 0 1 1 0 0 1 1 i
Encoding: 0 1 1 0 0 1 0 0 immediate data
Encoding: 0 1 1 0 0 0 1 0 direct address
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XRL direct, #data
Operation: XRL
(direct) ¬ (direct) ^ #data
Bytes: 3
Cycles: 2
Encoding: 0 1 1 0 0 0 1 1 direct address immediate data
Instruction Set Summary
Arithmetic Operations
Mnemonic Description Byte Cycle
ADD A, Rn Add register to accumulator 1 1
ADD A, direct Add direct byte to accumulator 2 1
ADD A, @Ri Add indirect RAM to accumulator 1 1
ADD A, data Add immediate data to accumulator 2 1
ADDC A, Rn Add register to accumulator with carry flag 1 1
ADDC A, direct Add direct byte to A with carry flag 2 1
ADDC A, @Ri Add indirect RAM to A with carry flag 1 1
ADDC A, #data Add immediate data to A with carry flag 2 1
SUBB A, Rn Subtract register from A with borrow 1 1
SUBB A, direct Subtract direct byte from A with borrow 2 1
SUBB A,@Ri Subtract indirect RAM from A with borrow 1 1
SUBB A, data Subtract immediate data from A with borrow 2 1
INC A Increment accumulator 1 1
INC Rn Increment register 1 1
INC direct Increment direct byte 2 1
INC @Ri Increment indirect RAM 1 1
DEC A Decrement accumulator 1 1
DEC Rn Decrement register 1 1
DEC direct Decrement direct byte 2 1
DEC @Ri Decrement indirect RAM 1 1
INC DPTR Increment data pointer 1 2
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MUL AB Multiply A and B 1 4
DIV AB Divide A by B 1 4
DA A Decimal adjust accumulator 1 1
Logic Operations
Mnemonic Description Byte Cycle
ANL A, Rn AND register to accumulator 1 1
ANL A, direct AND direct byte to accumulator 2 1
ANL A,@Ri AND indirect RAM to accumulator 1 1
ANL A, #data AND immediate data to accumulator 2 1
ANL direct, A AND accumulator to direct byte 2 1
ANL direct, #data AND immediate data to direct byte 3 2
ORL A, Rn OR register to accumulator 1 1
ORL A, direct OR direct byte to accumulator 2 1
ORL A,@Ri OR indirect RAM to accumulator 1 1
ORL A, #data OR immediate data to accumulator 2 1
ORL direct, A OR accumulator to direct byte 2 1
ORL direct, #data OR immediate data to direct byte 3 2
XRL A, Rn Exclusive OR register to accumulator 1 1
XRL A direct Exclusive OR direct byte to accumulator 2 1
XRL A,@Ri Exclusive OR indirect RAM to accumulator 1 1
XRL A, #data Exclusive OR immediate data to accumulator 2 1
XRL direct, A Exclusive OR accumulator to direct byte 2 1
XRL direct, #data Exclusive OR immediate data to direct byte 3 2
CLR A Clear accumulator 1 1
CPL A Complement accumulator 1 1
RL A Rotate accumulator left 1 1
RLC A Rotate accumulator left through carry 1 1
RR A Rotate accumulator right 1 1
RRC A Rotate accumulator right through carry 1 1
SWAP A Swap nibbles within the accumulator 1 1
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Data Transfer
*) MOV A, ACC is not a valid instruction
Mnemonic Description Byte Cycle
MOV A, Rn Move register to accumulator 1 1
MOV A, direct *) Move direct byte to accumulator 2 1
MOV A,@Ri Move indirect RAM to accumulator 1 1
MOV A, #data Move immediate data to accumulator 2 1
MOV Rn, A Move accumulator to register 1 1
MOV Rn, direct Move direct byte to register 2 2
MOV Rn, #data Move immediate data to register 2 1
MOV direct, A Move accumulator to direct byte 2 1
MOV direct, Rn Move register to direct byte 2 2
MOV direct, direct Move direct byte to direct byte 3 2
MOV direct,@Ri Move indirect RAM to direct byte 2 2
MOV direct, #data Move immediate data to direct byte 3 2
MOV @Ri, A Move accumulator to indirect RAM 1 1
MOV @Ri, direct Move direct byte to indirect RAM 2 2
MOV @Ri, #data Move immediate data to indirect RAM 2 1
MOV DPTR, #data16 Load data pointer with a 16-bit constant 3 2
MOVC A,@A + DPTR Move code byte relative to DPTR to accumulator 1 2
MOVC A,@A + PC Move code byte relative to PC to accumulator 1 2
MOVX A,@Ri Move external RAM (8-bit addr.) to A 1 2
MOVX A,@DPTR Move external RAM (16-bit addr.) to A 1 2
MOVX @Ri, A Move A to external RAM (8-bit addr.) 1 2
MOVX @DPTR, A Move A to external RAM (16-bit addr.) 1 2
PUSH direct Push direct byte onto stack 2 2
POP direct Pop direct byte from stack 2 2
XCH A, Rn Exchange register with accumulator 1 1
XCH A, direct Exchange direct byte with accumulator 2 1
XCH A,@Ri Exchange indirect RAM with accumulator 1 1
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XCHD A,@Ri Exchange low-order nibble indir. RAM with A 1 1
Boolean Variable Manipulation
Program and Machine Control
Mnemonic Description Byte Cycle
CLR C Clear carry flag 1 1
CLR bit Clear direct bit 2 1
SETB C Set carry flag 1 1
SETB bit Set direct bit 2 1
CPL C Complement carry flag 1 1
CPL bit Complement direct bit 2 1
ANL C, bit AND direct bit to carry flag 2 2
ANL C, /bit AND complement of direct bit to carry 2 2
ORL C, bit OR direct bit to carry flag 2 2
ORL C, /bit OR complement of direct bit to carry 2 2
MOV C, bit Move direct bit to carry flag 2 1
MOV bit, C Move carry flag to direct bit 2 2
ACALL addr11 Absolute subroutine call 2 2
LCALL addr16 Long subroutine call 3 2
RET Return from subroutine 1 2
RETI Return from interrupt 1 2
AJMP addr11 Absolute jump 2 2
LJMP addr16 Long jump 3 2
SJMP rel Short jump (relative addr.) 2 2
JMP @A + DPTR Jump indirect relative to the DPTR 1 2
JZ rel Jump if accumulator is zero 2 2
JNZ rel Jump if accumulator is not zero 2 2
JC rel Jump if carry flag is set 2 2
JNC rel Jump if carry flag is not set 2 2
JB bit, rel Jump if direct bit is set 3 2
JNB bit, rel Jump if direct bit is not set 3 2
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JBC bit, rel Jump if direct bit is set and clear bit 3 2
CJNE A, direct, rel Compare direct byte to A and jump if not equal 3 2
Mnemonic Description Byte Cycle
CJNE A, #data, rel Compare immediate to A and jump if not equal 3 2
CJNE Rn, #data rel Compare immed. to reg. and jump if not equal 3 2
CJNE @Ri, #data, rel Compare immed. to ind. and jump if not equal 3 2
DJNZ Rn, rel Decrement register and jump if not zero 2 2
DJNZ direct, rel Decrement direct byte and jump if not zero 3 2
NOP No operation 1 1
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ATMEL SERIES OF MICROCONTROLLERS
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LCD SECTION DETAILS:-
LCD DETAIL .
Frequently, an 8051 program must interact with the outside world using input and output
devices that communicate directly with a human being. One of the most common devices
attached to an 8051 is an LCD display. Some of the most common LCDs connected to
the 8051 are 16x2 and 20x2 displays. This means 16 characters per line by 2 lines and 20
characters per line by 2 lines, respectively.
Fortunately, a very popular standard exists which allows us to communicate with
the vast majority of LCDs regardless of their manufacturer. The standard is
referred to as HD44780U, which refers to the controller chip which receives data
from an external source (in this case, the 8051) and communicates directly with
the LCD.
44780 BACKGROUND
The 44780 standard requires 3 control lines as well as either 4 or 8 I/O lines for
the data bus. The user may select whether the LCD is to operate with a 4-bit data
bus or an 8-bit data bus. If a 4-bit data bus is used, the LCD will require a total of
7 data lines (3 control lines plus the 4 lines for the data bus). If an 8-bit data bus
is used, the LCD will require a total of 11 data lines (3 control lines plus the 8
lines for the data bus).
The three control lines are referred to as EN, RS, and RW.
The EN line is called "Enable." This control line is used to tell the LCD that you
are sending it data. To send data to the LCD, your program should first set this
line high (1) and then set the other two control lines and/or put data on the data
bus. When the other lines are completely ready, bring EN low (0) again. The 1-0
transition tells the 44780 to take the data currently found on the other control
lines and on the data bus and to treat it as a command.
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The RS line is the "Register Select" line. When RS is low (0), the data is to be
treated as a command or special instruction (such as clear screen, position
cursor, etc.). When RS is high (1), the data being sent is text data which should
be displayed on the screen. For example, to display the letter "T" on the screen
you would set RS high.
The RW line is the "Read/Write" control line. When RW is low (0), the information
on the data bus is being written to the LCD. When RW is high (1), the program is
effectively querying (or reading) the LCD. Only one instruction ("Get LCD status")
is a read command. All others are write commands--so RW will almost always be
low.
Finally, the data bus consists of 4 or 8 lines (depending on the mode of operation
selected by the user). In the case of an 8-bit data bus, the lines are referred to as
DB0, DB1, DB2, DB3, DB4, DB5, DB6, and DB7.
AN EXAMPLE HARDWARE CONFIGURATION
As we've mentioned, the LCD requires either 8 or 11 I/O lines to communicate
with. For the sake of this tutorial, we are going to use an 8-bit data bus--so we'll
be using 11 of the 8051's I/O pins to interface with the LCD.
Let's draw a sample psuedo-schematic of how the LCD will be connected to the
8051.
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As you can see, we've established a 1-to-1 relation between a pin on the 8051
and a line on the 44780 LCD. Thus as we write our assembly program to access
the LCD, we are going to equate constants to the 8051 ports so that we can refer
to the lines by their 44780 name as opposed to P0.1, P0.2, etc. Let's go ahead
and write our initial equates:
DB0 EQU P1.0
DB1 EQU P1.1
DB2 EQU P1.2
DB3 EQU P1.3
DB4 EQU P1.4
DB5 EQU P1.5
DB6 EQU P1.6
DB7 EQU P1.7
EN EQU P3.7
RS EQU P3.6
RW EQU P3.5
DATA EQU P1
Having established the above equates, we may now refer to our I/O lines by their 44780
name. For example, to set the RW line high (1), we can execute the following insutrction:
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SETB RW
HANDLING THE EN CONTROL LINE
As we mentioned above, the EN line is used to tell the LCD that you are ready for
it to execute an instruction that you've prepared on the data bus and on the other
control lines. Note that the EN line must be raised/lowered before/after each
instruction sent to the LCD regardless of whether that instruction is read or write,
text or instruction. In short, you must always manipulate EN when communicating
with the LCD. EN is the LCD's way of knowing that you are talking to it. If you
don't raise/lower EN, the LCD doesn't know you're talking to it on the other lines.
Thus, before we interact in any way with the LCD we will always bring the EN line
high with the following instruction:
SETB EN
And once we've finished setting up our instruction with the other control lines and data
bus lines, we'll always bring this line back low:
CLR EN
Programming Tip: The LCD interprets and executes our command at the instant
the EN line is brought low. If you never bring EN low, your instruction will never
be executed. Additionally, when you bring EN low and the LCD executes your
instruction, it requires a certain amount of time to execute the command. The time
it requires to execute an instruction depends on the instruction and the speed of
the crystal which is attached to the 44780's oscillator input.
CHECKING THE BUSY STATUS OF THE LCD
As previously mentioned, it takes a certain amount of time for each instruction to
be executed by the LCD. The delay varies depending on the frequency of the
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crystal attached to the oscillator input of the 44780 as well as the instruction
which is being executed.
While it is possible to write code that waits for a specific amount of time to allow
the LCD to execute instructions, this method of "waiting" is not very flexible. If the
crystal frequency is changed, the software will need to be modified. Additionally,
if the LCD itself is changed for another LCD which, although 44780 compatible,
requires more time to perform its operations, the program will not work until it is
properly modified.
A more robust method of programming is to use the "Get LCD Status" command
to determine whether the LCD is still busy executing the last instruction received.
The "Get LCD Status" command will return to us two tidbits of information; the
information that is useful to us right now is found in DB7. In summary, when we
issue the "Get LCD Status" command the LCD will immediately raise DB7 if it's
still busy executing a command or lower DB7 to indicate that the LCD is no
longer occupied. Thus our program can query the LCD until DB7 goes low,
indicating the LCD is no longer busy. At that point we are free to continue and
send the next command.
Since we will use this code every time we send an instruction to the LCD, it is
useful to make it a subroutine. Let's write the code:
WAIT_LCD:
SETB EN ;Start LCD command
CLR RS ;It's a command
SETB RW ;It's a read command
MOV DATA,#0FFh ;Set all pins to FF initially
MOV A,DATA ;Read the return value
JB ACC.7,WAIT_LCD ;If bit 7 high, LCD still busy
CLR EN ;Finish the command
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CLR RW ;Turn off RW for future commands
RET
Thus, our standard practice will be to send an instruction to the LCD and then call our
WAIT_LCD routine to wait until the instruction is completely executed by the LCD.
This will assure that our program gives the LCD the time it needs to execute instructions
and also makes our program compatible with any LCD, regardless of how fast or slow it
is.
Programming Tip: The above routine does the job of waiting for the LCD, but
were it to be used in a real application a very definite improvement would need to
be made: as written, if the LCD never becomes "not busy" the program will
effectively "hang," waiting for DB7 to go low. If this never happens, the program
will freeze. Of course, this should never happen and won't happen when the
hardware is working properly. But in a real application it would be wise to put
some kind of time limit on the delay--for example, a maximum of 256 attempts to
wait for the busy signal to go low. This would guarantee that even if the LCD
hardware fails, the program would not lock up.
INITIALIZING THE LCD
Before you may really use the LCD, you must initialize and configure it. This is
accomplished by sending a number of initialization instructions to the LCD.
The first instruction we send must tell the LCD whether we'll be communicating
with it with an 8-bit or 4-bit data bus. We also select a 5x8 dot character font.
These two options are selected by sending the command 38h to the LCD as a
command. As you will recall from the last section, we mentioned that the RS line
must be low if we are sending a command to the LCD. Thus, to send this 38h
command to the LCD we must execute the following 8051 instructions:
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SETB ENCLR RSMOV DATA,#38hCLR ENLCALL WAIT_LCD
Programming Tip: The LCD command 38h is really the sum of a number of
option bits. The instruction itself is the instruction 20h ("Function set"). However,
to this we add the values 10h to indicate an 8-bit data bus plus 08h to indicate that
the display is a two-line display.
We've now sent the first byte of the initialization sequence. The second byte of the
initialization sequence is the instruction 0Eh. Thus we must repeat the initialization code
from above, but now with the instruction. Thus the next code segment is:
SETB EN
CLR RS
MOV DATA,#0Eh
CLR EN
LCALL WAIT_LCD
Programming Tip: The command 0Eh is really the instruction 08h plus 04h to
turn the LCD on. To that an additional 02h is added in order to turn the cursor on.
The last byte we need to send is used to configure additional operational parameters of
the LCD. We must send the value 06h.
SETB EN
CLR RS
MOV DATA,#06h
CLR EN
LCALL WAIT_LCD
Programming Tip: The command 06h is really the instruction 04h plus 02h to
configure the LCD such that every time we send it a character, the cursor position
automatically moves to the right.
So, in all, our initialization code is as follows:
INIT_LCD:
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SETB EN
CLR RS
MOV DATA,#38h
CLR EN
LCALL WAIT_LCD
SETB EN
CLR RS
MOV DATA,#0Eh
CLR EN
LCALL WAIT_LCD
SETB EN
CLR RS
MOV DATA,#06h
CLR EN
LCALL WAIT_LCD
RET
Having executed this code the LCD will be fully initialized and ready for us to send
display data to it.
CLEARING THE DISPLAY
When the LCD is first initialized, the screen should automatically be cleared by
the 44780 controller. However, it's always a good idea to do things yourself so
that you can be completely sure that the display is the way you want it. Thus, it's
not a bad idea to clear the screen as the very first opreation after the LCD has
been initialiezd.
An LCD command exists to accomplish this function. Not suprisingly, it is the
command 01h. Since clearing the screen is a function we very likely will wish to
call more than once, it's a good idea to make it a subroutine:
CLEAR_LCD:
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SETB EN
CLR RS
MOV DATA,#01h
CLR EN
LCALL WAIT_LCD
RET
How that we've written a "Clear Screen" routine, we may clear the LCD at any time by
simply executing an LCALL CLEAR_LCD.
Programming Tip: Executing the "Clear Screen" instruction on the LCD also
positions the cursor in the upper left-hand corner as we would expect.
WRITING TEXT TO THE LCD
Now we get to the real meat of what we're trying to do: All this effort is really so
we can display text on the LCD. Really, we're pretty much done.
Once again, writing text to the LCD is something we'll almost certainly want to do
over and over--so let's make it a subroutine.
WRITE_TEXT:
SETB EN
SETB RS
MOV DATA,A
CLR EN
LCALL WAIT_LCD
RET
The WRITE_TEXT routine that we just wrote will send the character in the accumulator
to the LCD which will, in turn, display it. Thus to display text on the LCD all we need to
do is load the accumulator with the byte to display and make a call to this routine. Pretty
easy, huh?
A "HELLO WORLD" PROGRAM
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Now that we have all the component subroutines written, writing the classic
"Hello World" program--which displays the text "Hello World" on the LCD is a
relatively trivial matter. Consider:
LCALL INIT_LCD
LCALL CLEAR_LCD
MOV A,#'H'
LCALL WRITE_TEXT
MOV A,#'E'
LCALL WRITE_TEXT
MOV A,#'L'
LCALL WRITE_TEXT
MOV A,#'L'
LCALL WRITE_TEXT
MOV A,#'O'
LCALL WRITE_TEXT
MOV A,#' '
LCALL WRITE_TEXT
MOV A,#'W'
LCALL WRITE_TEXT
MOV A,#'O'
LCALL WRITE_TEXT
MOV A,#'R'
LCALL WRITE_TEXT
MOV A,#'L'
LCALL WRITE_TEXT
MOV A,#'D'
LCALL WRITE_TEXT
The above "Hello World" program should, when executed, initialize the LCD, clear the
LCD screen, and display "Hello World" in the upper left-hand corner of the display.
CURSOR POSITIONING
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The above "Hello World" program is simplistic in the sense that it prints its text in
the upper left-hand corner of the screen. However, what if we wanted to display
the word "Hello" in the upper left-hand corner but wanted to display the word
"World" on the second line at the tenth character? This sounds simple--and
actually, it is simple. However, it requires a little more understanding of the
design of the LCD.
The 44780 contains a certain amount of memory which is assigned to the
display. All the text we write to the 44780 is stored in this memory, and the 44780
subsequently reads this memory to display the text on the LCD itself. This
memory can be represented with the following "memory map":
Thus, the first character in the upper left-hand corner is at address 00h. The
following character position (character #2 on the first line) is address 01h, etc.
This continues until we reach the 16th character of the first line which is at
address 0Fh.
However, the first character of line 2, as shown in the memory map, is at address
40h. This means if we write a character to the last position of the first line and
then write a second character, the second character will not appear on the
second line. That is because the second character will effectively be written to
address 10h--but the second line begins at address 40h.
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Thus we need to send a command to the LCD that tells it to position the cursor
on the second line. The "Set Cursor Position" instruction is 80h. To this we must
add the address of the location where we wish to position the cursor. In our
example, we said we wanted to display "World" on the second line on the tenth
character position.
Referring again to the memory map, we see that the tenth character position of
the second line is address 4Ah. Thus, before writing the word "World" to the
LCD, we must send a "Set Cursor Position" instruction--the value of this
command will be 80h (the instruction code to position the cursor) plus the
address 4Ah. 80h + 4Ah = C4h. Thus sending the command C4h to the LCD will
position the cursor on the second line at the tenth character position:
SETB EN
CLR RS
MOV DATA,#0C4h
CLR EN
LCALL WAIT_LCD
The above code will position the cursor on line 2, character 10. To display "Hello" in the
upper left-hand corner with the word "World" on the second line at character position 10
just requires us to insert the above code into our existing "Hello World" program. This
results in the following:
LCALL INIT_LCD
LCALL CLEAR_LCD
MOV A,#'H'
LCALL WRITE_TEXT
MOV A,#'E'
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LCALL WRITE_TEXT
MOV A,#'L'
LCALL WRITE_TEXT
MOV A,#'L'
LCALL WRITE_TEXT
MOV A,#'O'
LCALL WRITE_TEXT
SETB EN
CLR RS
MOV DATA,#0C4h
CLR EN
LCALL WAIT_LCD
MOV A,#'W'
LCALL WRITE_TEXT
MOV A,#'O'
LCALL WRITE_TEXT
MOV A,#'R'
LCALL WRITE_TEXT
MOV A,#'L'
LCALL WRITE_TEXT
MOV A,#'D'
LCALL WRITE_TEXT
PIN WISE DETAIL OF LCD
1. Vss GROUND
2. Vcc +5VOLT SUPPLY
3 Vee POWER SUPPLY TO CONTROL CONTRAST
4. RS RS = 0 TO SELECT COMMAND REGISTER
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RS = 1 TO SELECT DATA REGISTER
5. R/W R/W = 0 FOR WRITER/W = 1 FOR READ
6 E ENABLE
7 DB0
8 DB1
9. DB2
10. DB3
11. DB4
12. DB5
13. DB6
14. DB7
15 ,16 FOR BACK LIGHT DISPLAY
LCD COMMAND CODES.
1. CLEAR DISPLAY SCREEN
2. RETURN HOME
4 DECREMENT CURSOR ( SHIFT CURSOR TO LEFT)
5 SHIFT DISPLAY RIGHT.
6. INCREMENT CURSOR ( SHIFT CURSOR TO RIGHT)
7. SHIFT DISPLAY LEFT
8. DISPLAY OFF, CURSOR OFF
A DISPLAY OFF CURSOR ON
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C DISPLAY ON CURSOR OFF
E DISPLAY ON CURSOR BLINKING
F. DISPLAY ON CURSOR BLINKING.
10. SHIFT CURSOR POSITION TO LEFT
14. SHIFT CURSOR POSITION TO RIGHT
18. SHIFT THE ENTIRE DISPLAY TO THE LEFT
1C SHIFT THE ENTIRE DISPLAY TO THE RIGHT
80 FORCE CURSOR TO BEGINNING OF IST LINE
C0 FORCE CURSOR TO BEGINNING OF 2ND LINE
38 2 LINES AND 5 X 7 MATRIX
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Flow Chart:-
Start
Initialize the I/O Ports, LCD, Variables, Timers
and Interruption
Display Message on LCD
Is Any Key?
Is Key = Measure
key?
Is Key = find speed
key?
Is Key = Reset key?
D
B
A
Reset the System Parameters
No
Yes
Yes
Yes
No
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Start
Initialize the I/O Ports, LCD, Variables, Timers
and Interruption
Display Message on LCD
Is Any Key?
Is Key = Measure
key?
Is Key = find speed
key?
Is Key = Reset key?
D
B
A
Reset the System Parameters
No
Yes
Yes
Yes
No
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A
Enable the Transmitter
Start the wait timer
Is Wait TimerOver?
Enable Receiver
Wait for the return Pulse
Is a Valid return pulse
Measure the time between pulse transmission & reception
Find out the distance in cm
Display the Distance on LCD
No
Yes
No
Yes
D
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Enable the Transmitter
Start the wait timer
Is Wait TimerOver?
Enable Receiver
Wait for the return Pulse
Is a Valid return pulse
Measure the time between pulse transmitted & received
Find out the speed in mtr /sec
Display the Speed on LCD
No
Yes
No
Yes
B
D
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Updated 8/17/98
Working With Stepper Motors Online Tutorial #1
This page is divided into several sections. Choose a section to jump to from the list, or scroll down to view the entire document.
Introduction - A general introduction to this document. Sources - Where to find stepper motors. Operation - How stepper motors work. Characteristics - Common characteristics of stepper motors. Types - Unipolar vs. Bipolar motor types of stepper motors. Translators - Example translator circuits. Software examples - Example code snippets for controlling stepper motors.
INTRODUCTIONI am by no means an expert on stepper motors. I have not completed my education, so I do not know all of the mathematics or mechanics that go into the design and operation of stepper motors. What I do know is what I have learned from my experience with these electro-mechanical wonders. This document willout line sources that carry stepper motors and how to control them manually (with discrete logic), with a microcontroller, and with computer control.
WHERE TO FIND STEPPER MOTORSStepper motors can be found in almost any piece of electro-mechanical equipment. From my personal experiences, good sources for stepper motors include:
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Surplus dot-matrix printersIf you find one of these at a swap meet, surplus store, or garage sale for a good price, buy it! They usually contain at least 2 motors, sometimes with optical shaft encoders attached to the motors! Also a good source for matching gears and toothed belts. As a general rule, larger printers will have larger, more powerful stepper motors in them.
Old floppy disk drivesThese usually contain at least 1 stepper motor, and if you're fortunate, possibly a driver IC that can be salvaged and re-used in your own projects. Along with the motor you will get some optical interrupter units used by the drive to sense the state of the write-protect tabs and to index the disk.
Surplus storesThese places buy surplus from others and sell it to the public, often at great prices. The average price for a small to medium stepper motor is usually around $5.00.
Mail Order CompaniesYou can find surplus motors or even new, packaged units. Naturally the new units are going to cost more, but this may save time and money if you're building equipment with the motors that will be used at more than a "hobby" level. For general tinkering and small scale robotics, used motors will work just fine.
HOW STEPPER MOTORS WORKWe've all experimented with small "hobby motors", or free-spinning DC motors. Have you ever tried to position something accurately with one? It can be pretty difficult. Even if you get the timing just right for starting and stopping the motor, the armature does not stop immediately. DC motors have a very gradual acceleration and deceleration curves; stabilization is slow. Adding gearing to the motor will help to reduce this problem, but overshoot is still present and will throw off the anticipated stop position. The only way to effectively use a DC motor for precise positioning is to use a servo. Servos usually implement a small DC motor, a feedback mechanism (usually a potentiometer with attached to the shaft by gearing or other means), and a control circuit which compares the position of the motor with the desired position, and moves the motor accordingly. This can get fairly complex and expensive for most hobby applications.
Stepper motors, however, behave differently than standard DC motors. First of all, they cannot run freely by themselves. Stepper motors do as their name suggests -- they "step" a little bit at a time.Stepper motors also differ from DC motors in their torque-speed relationship. DC motors generally are not very good at producing high torque at low speeds, without the aid of a gearing mechanism. Stepper motors, on the other hand, work in the opposite manner. They produce the highest torque at lowspeeds. Stepper motors also have another characteristic, holding torque, which is not present in DC motors. Holding torque allows a stepper motor to hold its position firmly when not turning. This can be useful for applications where the motor may be starting and stopping, while the force acting against the motor remains present. This eliminates the need for a mechanical brake mechanism. Steppers don't simply respond to a clock signal, they have several windings which need to be energized in the correct sequence before the motor's shaft will rotate. Reversing the order of the sequence will cause the motor to rotate the other way. If the control signals are not sent in the correct order, the motor will not turn properly. It may simply buzz and not move, or it may actually turn, but in a rough or jerky manner. A circuit which is responsible for
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converting step and direction signals into winding energization patterns is called a translator. Most stepper motor control systems include adriver in addition to the translator, to handle the current drawn by the motor's windings.
Figure 1.1 - A typical translator / driver connection
A basic example of the "translator + driver" type of configuration. Notice the separate voltages for logic and for the stepper motor. Usually the motor will require a different voltage than the logic portion of the system. Typically logic voltage is +5 Vdc and the stepper motor voltage can range from +5 Vdc up to about +48 Vdc. The driver is also an "open collector" driver, wherein it takes its outputs to GND to activate the motor's windings. Most semiconductor circuits are more capable of sinking(providing a GND or negative voltage) than sourcing (outputting a positive voltage).
COMMON CHARACTERISTICS OF STEPPER MOTORS:Stepper motors are not just rated by voltage. The following elements characterize a given steppermotor:
VoltageStepper motors usually have a voltage rating. This is either printed directly on the unit, or is specified in the motor's datasheet. Exceeding the rated voltage is sometimes necessary to obtain the desired torque from a given motor, but doing so may produce excessive heat and/or shorten the life of the motor.
ResistanceResistance-per-winding is another characteristic of a stepper motor. This resistance will determine current draw of the motor, as well as affect the motor's torque curve and maximum operating speed.
Degrees per stepThis is often the most important factor in choosing a stepper motor for a given application. This factor specifies the number of degrees the shaft will rotate for each full step. Half step operation of the motor will double the number of steps/revolution, and cut the degrees-per-step in half. For unmarked motors, it is often possible to carefully count, by hand, the number of steps per revolution of the motor. The degrees per step can be calculated by dividing 360 by the number of steps in 1 complete revolution Common degree/step numbers include: 0.72, 1.8, 3.6, 7.5, 15, and even 90. Degrees per step is often referred to as the resolution of the motor. As in the case of an unmarked motor, if a motor has only the number of steps/revolution printed on it, dividing 360 by this number will yield the degree/step value.
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TYPES OF STEPPER MOTORSStepper motors fall into two basic categories: Permanent magnet and variable reluctance. The type of motor determines the type of drivers, and the type of translator used. Of the permanent magnet stepper motors, there are several "subflavors" available. These include the Unipolar, Bipolar, and Multiphase varieties.
Permanent Magnet Stepper Motors
Unipolar Stepper MotorsUnipolar motors are relatively easy to control. A simple 1-of-'n' counter circuit can generate the proper stepping sequence, and drivers as simple as 1 transistor per winding are possible with unipolar motors. Unipolar stepper motors are characterized by their center-tapped windings. A common wiring scheme is to take all the taps of the center-tapped windings and feed them +MV (Motor voltage). The driver circuit would then ground each winding to energize it.
Figure 2.1 - A typical unipolar stepper motor driver circuit. Note the 4 back EMF protection diodes.
Unipolar stepper motors are recognized by their center-tapped windings. The number of phases is twice the number of coils, since each coil is divided in two. So the diagram below (Figure 3.1), which has two center-tapped coils, represents the connection of a 4-phase unipolar stepper motor.
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Figure 3.1 - Unipolar stepper motor coil setup (left) and 1-phase drive pattern (right).
In addition to the standard drive sequence, high-torque and half-step drive sequences are also possible. In the high-torque sequence, two windings are active at a time for each motor step. This two-winding combination yields around 1.5 times more torque than the standard sequence, but it draws twice the current. Half-stepping is achieved by combining the two sequences. First, one of the windings is activated, then two, then one, etc. This effectively doubles the number of steps the motor will advance for each revolution of the shaft, and it cuts the number of degrees per step in half.
Full-stepping animation Half-stepping animation
Figure 4.1 - Two-phase stepping sequence (left) and half-stepsequence (right).
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Click on the links above the figure to see animated demonstrations.
Bipolar Stepper MotorsUnlike unipolar stepper motors, Bipolar units require more complex driver circuitry. Bipolar motorsare known for their excellent size/torque ratio, and provide more torque for their size than unipolar motors. Bipolar motors are designed with separate coils that need to be driven in either direction (the polarity needs to be reversed during operation) for proper stepping to occur. This presents a driver challenge. Bipolar stepper motors use the same binary drive pattern as a unipolar motor, only the '0' and '1' signals correspond to the polarity of the voltage applied to the coils, not simply 'on-off' signals. Figure 5.1 shows a basic 4-phase bipolar motor's coil setup and drive sequence.
Figure 5.1 - Bipolar stepper motor coil setup (left) and drive pattern (right).
A circuit known as an "H-bridge" (shown below) is used to drive Bipolar stepper motors. Each coil of the stepper motor needs its own H-bridge driver circuit. Typical bipolar steppers have 4 leads, connected to two isolated coils in the motor. ICs specifically designed to drive bipolar steppers (or DC motors) are available (Popular are the L297/298 series from ST Microelectronics, and the LMD18T245 from National Semiconductor). Usually these IC modules only contain a single H-bridge circuit inside of them, so two of them are required for driving a single bipolar motor. One problem with the basic (transistor) H-bridge circuit is that with a certain combination of input values (both '1's) the result is that the power supply feeding the motor becomes shorted by the transistors. This could cause a situation where the transistors and/or power supply may be destroyed. A small XOR logic circuit was added in figure 6.1 to keep both inputs from being seen as '1's by the transistors.
Another characteristic of H-bridge circuits is that they have electrical "brakes" that can be applied to slow or even stop the motor from spinning freely when not moving under control by the driver circuit. This is accomplished by essentially shorting the coil(s) of the motor together, causing any voltage produced in the coils by during rotation to "fold back" on itself and make the shaft difficult to turn. The faster the shaft is made to turn, the more the electrical "brakes" tighten.
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Figure 6.1 - A typical H-Bridge circuit. The 4 diodes clamp inductive kickback.
Variable Reluctance Stepper MotorsSometimes referred to as Hybrid motors, variable reluctance stepper motors are the simplest to control over other types of stepper motors. Their drive sequence is simply to energize each of the windings in order, one after the other (see drive pattern table below) This type of stepper motor will often have only one lead, which is the common lead for all the other leads. This type of motor feels like a DC motor when the shaft is spun by hand; it turns freely and you cannot feel the steps. This type of stepper motor is not permanently magnetized like its unipolar and bipolar counterparts.
Figure 7.1 - Variable reluctance stepper motor coil setup (left) and drive pattern (right).
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EXAMPLE TRANSLATOR CIRCUITSIn this section, I will show examples of basic stepper motor translation circuits. Not all of these examples have been tested, so be sure to prototype the circuit before soldering anything.
Figure 8.1 illustrates the simplest solution to generating a one-phase drive sequence. For unipolar stepper motors, the circuit in Figure 2.1, or for bipolar stepper motors, the circuit in Figure 6.1 can be connected to the 4 outputs of this circuit to provide a complete translator + driver solution. This circuit is limited in that it cannot reverse the direction of the motor. This circuit would be most useful in applications where the motor does not need to change directions.
Figure 8.1 - A simple, single direction, single phase drive translator.
Figure 9.1 is an translator for two-phase operation. I have seen this circuit many places, but I believe it originated from The Robot Builders' Bonanza book, by Gordon McComb. I have used this circuit in the past and seem to recall that it had a problem. This may not be the case but I think when you reverse direction and continue stepping, the motor will advance 1 more step in the previous direction it was going before responding. As always, prototype this circuit to be sure it will work for your application before you build anything with it.
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Figure 9.1 - A simple, bidirectional, two-phase drive stepper motor translator circuit.
There are several standard stepper motor translation circuits which use discrete logic ICs. Below you will find yet another one of these. The circuit in Figure 10.1 has not been tested but theoretically should work without problems.
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Figure 10.1 - Another example of a two-phase drive translator circuit, this time using a multiplexer.
CONTROL SOFTWARE EXAMPLESBelow you will find some small pieces of code, mostly in C/C++, some in Assembly language for various processors and microcontrollers. This code is by no means complete, but is provided only to give a basic understanding of the software involved in controlling stepper motors both with and without the use of a hardware translator circuit.
Words of caution:When making connections to either a PC parallel port, or I/O pins of a microcontroller, be sure to isolate the motor well. High voltage spikes of several hundered volts are possible as back EMF from stepper motor coils. Always use clamping diodes to short these spikes back to the motor's power bus. The use of optical isolation devices (optoisolators) will add yet another layer or protection between the delicate control logic and the high-voltage potentials which may be present in the power output stage. Whenever possible, use separate power supplies for the motor and the translator / microcontroller. This further reduces the chance of destructive voltages reaching the controller, and reduces or eliminates power supply noise that may be introduced by the motor.
If you're using a computer that has a parallel port as part of its onboard I/O, you may want to
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consider purchasing a parallel port card to use instead. I've seen them for as little as $9.99 at Fry's Electronics and other computer stores. Not only does this reduce the risk of permanently damaging or destroying your motherboard (it happened to a friend of mine!), but it will also allow you to experiment without the need for swapping cables or flipping a switchbox when you want to use your parallel printer, since your experiments won't be sharing its port. It is much cheaper to throw out a $10.00 parallel port card than it is to replace your motherboard!
Complete Software Control:Under complete software control, there is no translator circuit external to the Parallel port or microcontroller. This scheme reduces parts count, component cost, and makes for simpler board design. On the other hand, it places the responsibility of generating all of the sequencing signals on the software. If the PC or microcontroller is not fast enough (due to code inefficiency or slow processor speed), or too many motors are driven simultaneously, things can begin to slow down. Interrupts and other system events can plague the control software more in this case. Despite the downfalls of addressing a stepper motor directly in this manner, it is definitely the easiest and most straightforward approach to controlling a stepper motor. This method of controlling a motor can also be useful where the hardware is not critical at first and a simple interface is needed to allow more time to be spent on the development of the software before the hardware is refined.
Unless otherwise indicated, all material on this site is the original work of Jason Johnson.Copyright © 1998 Jason Johnson
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CIRCUIT WORKING OF STEPPER MOTOR CONTROL.
In this project when we interface the data from the computer then firstly we interface the
circuit with the optocoupler. In optocoupler circuit we use ic 817 optocoupler. Here we
use four optocoupler with this circuit. Output of the optpcoupler is negative. So to
convert this negative output to the positive we use one inverter ic. In this project we use
ic 4049 as a inverter. Pin no 3,5,7,9,11 is the input pin and pin no 2,4,6,10, 12 is the
output pin. . from the output pin we interface the transistor circuit. Here we use NPN
transistor. Emitter of the NPN transistor is connected to the negative voltage. Collector of
the NPN transistor is connected to the coil of the stepper motor . Here we use total four
transistor’s . collector of the transistor is connected to the each coil of the stepper motor.
Now with the help of the
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$include (reg51xa.INC)
LCD_DATA equ P0
lcd_en bit P2.5
lcd_rw bit P2.6
lcd_rs bit P2.7
key1 bit p2.0
output bit p3.6
FLAG equ 20h
flag0 bit FLAG.0
PULSL equ 22h
PULSH equ 23h
des_contr equ 2Fh
org 0000h
ljmp main
org 0003h
reti
org 000bh
reti
org 0013h
reti
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org 001bh
reti
org 0023h
reti
main:
mov psw,#00h
mov sp,#070h
mov tmod,#01h
mov tcon,#00h
mov scon,#00h
mov ie,#08h
mov ip,#08h
mov p0,#00h
mov p1,#0ffh
mov p2,#0ffh
mov p3,#0ffh
mov delayr0,#00h
mov delayr1,#00h
mov PULSL,#00h
mov PULSH,#00h
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clr lcd_rs
clr lcd_rw
clr lcd_en
clr flag0
lcall DELAY41
lcall DELAY41
lcall INIT_LCD
lcall CLR_LCD
mov dptr,#MSG0
lcall LINE_1
mov dptr,#MSG1
lcall LINE_2
lcall DELAY41
lcall DELAY41
BEG1:
lcall DELAY41
jb key1,BEG1
lcall DELAY41
jb key1,BEG1
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BEG:
MOV TH0,#0
MOV TL0,#0
pulse: setb p3.0
mov r1,#12
djnz r1,$
clr p3.0
mov r1,#5
djnz r1,
djnz r2, pulse
setb tr0
clr p3.2
mov r2,#20
djnz r2,$
setb p3.2
lp2:
jb p3.1,lp1
clr tr0
mov dptr,#MSG2
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lcall LINE_2
lcall DELAY41
lcall DELAY41
mov r0,TL0
mov r1,TH0
mov r2,#58
mov r3,#0
call UDIV16
clr c
mov a,r0
add a,#18d
mov r0,a
mov a,r1
addc a,#0d
mov r1,a
mov PULSH,r1
mov PULSL,r0
call disp1
lcall DELAY41
lcall DELAY41
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clr output
mov p1,#0ffh
jmp beg1
lp1:
mov a,th0
cjne a,#17h,lp2
mov dptr,#MSG3
lcall LINE_2
setb output
nxt_up: jb flag0,nxt_dn
mov a,des_contr
inc a
cjne a,#200d,nxt_step
setb flag0
sjmp nxt_step
nxt_dn: jnb flag0,nxt_up
mov a,des_contr
dec a
cjne a,#0d,nxt_step
clr flag0
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sjmp nxt_step
nxt_step:
mov des_contr,a
anl a,#03h
cjne a,#3d,nxt_step1
mov p1,#3d
nxt_step1:
cjne a,#2d,nxt_step2
mov p1,#6d
nxt_step2:
cjne a,#1d,nxt_step3
mov p1,#12d
nxt_step3:
cjne a,#0d,nxt_step4
mov p1,#9d
nxt_step4:
lcall DELAY41
lcall DELAY41
jmp beg
UDIV16: mov r7,#0
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mov r6,#0
mov B,#16
div_loop:
mov a,r7
div_1: mov a,r4
rlc a
mov r4,a
mov a,r5
rlc a
mov r5,a
djnz B,div_loop
mov a,r5
mov r1,a
mov a,r4
mov r0,a
mov a,r7
mov r3,a
mov a,r6
mov r2,a
ret
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Hex2BCD:
MOV R3,#00D
MOV R4,#00D
MOV R5,#00D
MOV R6,#00D
MOV R7,#00D
MOV B,#10D
MOV A,R2
DIV AB
MOV R3,B
MOV B,#10
DIV AB
MOV R4,B
MOV R5,A
CJNE R1,#0H,HIGH_BYTE
SJMP ENDD
HIGH_BYTE:
MOV A,#6
ADD A,R3
MOV B,#10
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DIV AB
MOV R3,B
ADD A,#5
ADD A,R4
MOV B,#10
DIV AB
MOV R4,B
ADD A,#2
ADD A,R5
MOV B,#10
DIV AB
MOV R5,B
CJNE R6,#00D,ADD_IT
SJMP CONTINUE
ADD_IT: ADD A,R6
CONTINUE:
MOV R6,A
DJNZ R1,HIGH_BYTE
MOV B, #10D
MOV A,R6
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DIV AB
MOV R6,B
MOV R7,A
ENDD: ret
DISP1:
mov r1,PULSH
mov r2,PULSL
LCALL HEX2BCD
MOV dp1,r3
MOV dp2,r4
MOV dp3,r5
mov LCD_DATA,#0cch
lcall COMMAND_BYTE
ADD a,#30h
mov LCD_DATA,a
lcall DATA_BYTE
mov LCD_DATA,#0cdh
lcall COMMAND_BYTE
mov a,dp2
ADD a,#30h
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mov LCD_DATA,a
lcall DATA_BYTE
mov LCD_DATA,#0ceh
lcall COMMAND_BYTE
mov LCD_DATA,a
lcall DATA_BYTE
mov a,des_contr
mov b,#18d
mul ab
mov r1,b
mov r2,a
LCALL HEX2BCD
MOV dp4,r3
MOV dp5,r4
MOV dp6,r5
MOV dp7,r6
mov LCD_DATA,#0c3h
lcall COMMAND_BYTE
mov a,dp7
ADD a,#30h
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mov LCD_DATA,a
lcall DATA_BYTE
mov LCD_DATA,#0c4h
lcall COMMAND_BYTE
mov a,dp6
ADD a,#30h
mov LCD_DATA,a
lcall DATA_BYTE
mov LCD_DATA,#0c5h
lcall COMMAND_BYTE
mov a,dp5
ADD a,#30h
mov LCD_DATA,a
lcall DATA_BYTE
mov LCD_DATA,#0c6h
lcall COMMAND_BYTE
mov LCD_DATA,#'.'
lcall DATA_BYTE
mov LCD_DATA,#0c7h
lcall COMMAND_BYTE
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mov a,dp4
ADD a,#30h
mov LCD_DATA,a
lcall DATA_BYTE
ret
LINE_1:
mov LCD_DATA,#080h
lcall COMMAND_BYTE
lcall DELAY1
lcall WRITE_MSG
ret
LINE_2:
mov LCD_DATA,#0c0h
lcall COMMAND_BYTE
lcall DELAY1
lcall WRITE_MSG
ret
INIT_LCD:
mov LCD_DATA,#00h
lcall COMMAND_BYTE
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lcall DELAY1
mov LCD_DATA,#00h
lcall COMMAND_BYTE
lcall DELAY1
mov LCD_DATA,#038h
lcall COMMAND_BYTE
lcall DELAY1
mov LCD_DATA,#038h
lcall COMMAND_BYTE
lcall DELAY1
mov LCD_DATA,#038h
lcall COMMAND_BYTE
lcall DELAY1
mov LCD_DATA,#038h
lcall COMMAND_BYTE
lcall DELAY1
mov LCD_DATA,#008h
lcall COMMAND_BYTE
lcall DELAY1
mov LCD_DATA,#00ch
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lcall COMMAND_BYTE
lcall DELAY1
mov LCD_DATA,#006h
lcall COMMAND_BYTE
lcall DELAY1
ret
CLR_LCD:
mov LCD_DATA,#001h
lcall COMMAND_BYTE
lcall DELAY1
ret
WRITE_MSG:
mov a,#00h
movc a,@a+dptr
cjne a,#'$',WRITE_CONT
ret
WRITE_CONT:
mov LCD_DATA,a
lcall DATA_BYTE
inc dptr
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ljmp WRITE_MSG
COMMAND_BYTE:
clr lcd_rs
lcall DELAY
ljmp CMD10
DATA_BYTE:
setb lcd_rs
lcall DELAY
CMD10:
clr lcd_rw
lcall DELAY
setb lcd_en
lcall DELAY
clr lcd_en
lcall DELAY41
ret
DELAY:
mov delayr0,#10d
DEL:
djnz delayr0,DEL
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ret
DELAY1:
mov delayr0,#0d
mov delayr1,#20d
DELAY10:
djnz delayr0,DELAY10
djnz delayr1,DELAY10
ret
DELAY41:
mov delayr0,#0d
mov delayr1,#15d
DLP410:
djnz delayr0,DLP410
djnz delayr1,DLP410
ret
MSG0: db 'Ultrasonic Radar$'
MSG1: db 'DES.+ DIS. Meter$'
MSG2: db 'De Di $'
MSG3: db ' Search Range $'
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END