Lecture note 7 AVR Advanced Assembly Language Programming Different Addressing Modes · 2015. 2....

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AVR Advanced Assembly Language Programming Different Addressing Modes

University of Kashan

Faculty of Electrical and Computer Engineering

Department of Computer Engineering

Hossein Sabaghian-Bidgoli

[email protected]

Fall 2014

Lecture note 7

Assembler Directives

University of Kashan Microprocessors 2

.INCLUDE, .ORG, .EQU, .SET, .DEF

Arithmetic Expression (+-*/%)

Logic Expression (&|^~)

Shift Operators (<<, >>)

mailto:[email protected]

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An Application of Shift Operators (<<, >>)



HIGH() and LOW() Functions



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Addressing Modes


Data Immediate Register Memory

Data memory Direct Register Indirect (Auto inc, Auto Dec, With displacement)

Program memory Indirect ((Auto inc)

EEPROM

IO Direct

Bit

Program (label) Absolute (long) Relative(Short) Indirect

Addressing Modes


Single Register Addressing

Immediate Addressing

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Addressing Modes


Two Register Addressing

Addressing Modes


Data Direct Addressing

Examples: STS 0x1000,R16

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Addressing Modes


IO Direct Addressing


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Register Indirect

Examples: LD R16, Y

ST Z, R16


Register Indirect

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Addressing Modes


Register Indirect with Pre-Decrement

Examples: LD R16, -Z

ST -Z, R16

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Addressing Modes


Register Indirect with Post-Increment

Examples: LD R16, Z+

ST Z+, R16

Addressing Modes


Register Indirect With Displacement

Examples: LDD R16, Y+0x10

STD Z+0x20, R16

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Addressing Modes


Register Indirect

Look up Table


.DB Define Bytes in program memory

Program memory is word addressable

Assembler align to even address

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Look up Table


.DW

Define Words in program memory

Addressing Modes


Program Memory Addressing

Examples: LPM Rn, Z

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Addressing Modes


Program Memory Addressing with Post Increment

Examples: LPM Rn, Z+

Addressing Modes


Indirect Program Addressing

Examples: IJMP

ICALL

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Addressing Modes


Relative Program Addressing

Examples: RJMP

RCALL

Look up Table


The value of Z

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Look up Table


The value of Z


Read a string from flash and send to output PortB

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Example 6-17


Read a string from flash memory char by char , Write them to SRAM

Example 6-18


Get a 3-bit number from PortC , Put corresponding Ascii code to PortD

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Example 6-19


Get a 4-bit number x from PortB , catch x2 from a look-up table, put to PortD

Example 6-20


Get a 4-bit number x from PortB , put x2+2x+3 to PortC (Use a look-up table)

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LED on the Output Ports


Correct cases Case1: LED is ON if output=zero Case2: LED is ON if output=One Most LEDs drop 1.7 volts and need about 10ma Current is (5-1.7)/470

Incorrect cases Case3 and case4:

Too much current

Failure of Port or LED

Case5: LED is ON if output=1 Appropriate for open collector output (NPN)

Else (if no open collector) failure of Port or LED when 1

High power consumption

Case6: LED is ON if output=0 Appropriate for open collector output (PNP)

Else (if no open collector) failure of Port or LED when 0

High power consumption

Output Pin

Vcc=+5V

470

Output Pin

Vcc=+5V

470

Output Pin

Vcc=+5V Output Pin

Output Pin

Vcc=+5V

470

Output Pin

Case2

Case1

Case4

Case3

Case5 Case6

OK

The 7-segment Display (Cont.)

7-segment displays come in 2 configurations:

Common Anode Common Cathode

Connect cathodes to the output Connect Anode to the output

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BCD to 7_Seg lookup table


BCD p g f e d c b a

7_seg

hex

0000 0 0 1 1 1 1 1 1 3f

0001 0 0 1 1 0 0 0 0 30

0010 0 1 0 1 1 0 1 1 5b

0011 0 1 0 0 1 1 1 1 4f

0100 0 1 1 0 0 1 1 0 66

0101 0 1 1 0 1 1 0 1 6d

0110 0 1 1 1 1 1 0 1 7d

0111 0 0 0 0 0 1 1 1 07

1000 0 1 1 1 1 1 1 1 7f

1001 0 1 1 0 1 1 1 1 6f

e

f

a

b

c

f

d

f

e

a

b

e

g

d

a

b

c

g

d

b

c

f g

a

c

g

d

a

c

f

e

g

d

a

b

c

a

b

c

f

e

g

d

a

b

c

f g

d

a

b

c

f

e

g

d

tab_7sg: .db 0x3f,0x30,0x5b,0x4f,0x66, 0x6d

.db 0x7d,0x07,0x7f,0x6f

Example: Read Data from SRAM


.include "m16def.inc"

.org 0

LDI R17, High(RAMEND)

OUT SPH, R17

LDI R17, LOW(RAMEND)

OUT SPL, R17

LDI R17, 0b00000110

STS 0x60, R17

LDI R17, 0b01001111

STS 0x61, R17

LDI R17, 0b11101111

STS 0x62, R17

LDI R17, 0b01001111

STS 0x63, R17 ;--->

;--->

LDI R17, 0xff

OUT DDRC, R17

REPEAT:

LDI YL, 0x60

LDI YH, 0x00

LDI R16, 4

UP:

LD R17, Y+

OUT PORTC,R17

CALL DELAY

DEC R16

BRNE UP

jmp REPEAT

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Example: Read Data from SRAM



.org 0


OUT SPH, R17


OUT SPL, R17

LDI R17, 0b00000110

STS 0x60, R17

LDI R17, 0b01001111

STS 0x61, R17

LDI R17, 0b11101111

STS 0x62, R17

LDI R17, 0b01001111

STS 0x63, R17 ;--->

;--->

LDI R17, 0xff

OUT DDRC, R17

REPEAT:

LDI YL, 0x60

LDI YH, 0x00

LDI R16, 4

UP:

LD R17, Y+

OUT PORTC,R17

CALL DELAY

DEC R16

BRNE UP

jmp REPEAT

Example: Read Data from Code Memory



.org 0


OUT SPH, R17


OUT SPL, R17

LDI R17, 0b00000110

STS 0x60, R17

LDI R17, 0b01001111

STS 0x61, R17

LDI R17, 0b11101111

STS 0x62, R17

LDI R17, 0b01001111

STS 0x63, R17 ;--->

;---> LDI R17, 0xff

OUT DDRC, R17

REPEAT:

LDI ZL, LOW(Data1<<1)

LDI ZH, HIGH(Data1<<1)

LDI R16, 4

UP:

LPM R17, Z+

OUT PORTC,R17

CALL DELAY

DEC R16

BRNE UP

jmp REPEAT

.ORG 0x050

Data1: .DB 0b00000110,0b01001111

.DB 0b01101111,0b01001111

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Example: Read Data from Code Memory



.org 0


OUT SPH, R17


OUT SPL, R17

LDI R17, 0b00000110

STS 0x60, R17

LDI R17, 0b01001111

STS 0x61, R17

LDI R17, 0b11101111

STS 0x62, R17

LDI R17, 0b01001111

STS 0x63, R17 ;--->

;---> LDI R17, 0xff

OUT DDRC, R17

REPEAT:



LDI R16, 4

UP:

LPM R17, Z+

OUT PORTC,R17

CALL DELAY

DEC R16

BRNE UP

jmp REPEAT

.ORG 0x050

Data1: .DB 0x06,0x4f,0x6f,0x4f

Example: Look-up Table



.org 0


OUT SPH, R17


OUT SPL, R17

LDI R17, 1

STS 0x60, R17

LDI R17, 3

STS 0x61, R17

LDI R17, 9

STS 0x62, R17

LDI R17, 3

STS 0x63, R17 ;--->

;--->

LDI R17, 0xff

OUT DDRC, R17

REPEAT:

LDI YL, 0x60

LDI YH, 0x00


LDI R16, 4

UP:


LD R17, Y+

ADD ZL, R17

LPM R17, Z

OUT PORTC,R17

CALL DELAY

DEC R16

BRNE UP

jmp REPEAT

.ORG 0x050

Data1: .DB 0,0x06,0,0x4f,0,0,

.DB 0,0,0,0x6f,0x4f

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Multiplexing of 7_seg


LED Matrix (8×8)


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Bit Addressing Modes


How to manipulate bits of GPRs? Using a Mask Selective set

ORI Rd, K ;RdRd or K (K is an 8 bit immediate) SBR Rd, K ;RdRd or K Different name for just one instruction

Selective clear ANI Rd, K ;RdRd and K (K is an 8 bit immediate) CBR Rd, K ;RdRd and K Different name for just one instruction

Examples

LDI R16, 0b01011001 SBR R16, 0b01100100 ;R16=0b01111101 CBR R16, 0b11110000 ;R16=0b01110000



How to manipulate a bit of I/O Registers? Use Bit Addressing Set a bit

SBI A, b ;Set bit b in I/O register with address A SBI PortC, 2 ;PortC_Bit21

Clear a bit CBI A, b ;Clear bit b in I/O register with address A CBI PortC, 2 ;PortC_Bit20

How to copy a bit from a GPR to another GPR? Use Bit Addressing Store a bit

BST Rr, b ;Store bit b of Rr in T flag of SREG

Load a bit BLD Rd, b ;Load bit from T to bit b of Rd

Example BST R17, 3 BLD R19, 5 ;Copy R17_3 to R19_5

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LDS R16, MYREG

4



Bit Addressing always is direct adressing

Bit addressing instructions

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How to check a bit? Use Skip with bit addressing Check a bit of IO register

SBIS A, b SBIS PortC, 2 ;If (PortC_Bit2==1) Skip next instruction

SBIC A, b SBIC PortB, 5 ;If (PortB_Bit5==0) Skip next instruction

Check a bit of GPR SBRS Rn, b

SBRS R20, 3 ;If (R20_Bit3==1) Skip next instruction SBRC Rn, b

SBRC R3, 7 ;If (R3_Bit7==0) Skip next instruction

Use Branch with bit addressing Check a bit of SREG

BRBS s, k BRBS 0, LBL1 ;If (C==1) jump to LBL1 else go to next instruction

BRBC s, k BRBC 4, Neg ;If (S==0) jump to Neg else go to next instruction



How to check a bit?

Use Skip with bit addressing Check a bit of IO register Check a bit of GPR

Use Branch with bit addressing Check a bit of SREG (BRBS,BRBC) Use specific instruction

BRBS BRBC

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How to manipulate a bit of SREG? Use Set and Clear instruction with bit addressing mode BSET s ;Set bit s of SREG BCLR s ;Clear bit s of SREG

Use specific instruction Below instructions

BSET BCLR


SBIS

SBIS PINC, 7

6-25

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SBIC PINC, 7

R

SBIC



How to manipulate a bit of SRAM? Answer: SRAM is not bit addressable Load a byte from SRAM to a GPR Then manipulate or check it

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Accessing EEPROM in AVR


SRAM is volatile

Flash is read only at run time

Write data into EEPROM to protect against power cut off

3 IO register EECR EEPROM Control Register

EEDR EEPROM Data Register

EEAR (EEARH and EEARL) EEPROM Address Register



ATmega32 1 KB EEPROM 10 bit address (EEAR9:EEAR0)

ATmega16 512 B EEPROM 9 bit address (EEAR8:EEAR0)

ATmega64 2 KB EEPROM 11 bit address (EEAR11:EEAR0)

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EECR is used to select the operation read or write

EERE: EEPROM Read Enable

EEWE: EEPROM Write Enable

EEMWE: EEPROM Master Write Enable If is set by user will be clear by hardware after 4 clock cycle

Write is started if both EEWE and EEMWE are 1

We can not start a read or write before last write is finished

When write is finished EEWE is cleared by hardware

Check it by polling



Write algorithm

Wait until EEWE become 0

Put address to EEAR (EEARH and EEARL)

Put data to EEDR

Set EEMWE to 1

Set EEWE to 1 (within 4 cycle after setting EEMWE)

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Read algorithm

Wait until EEWE become 0

Put address to EEAR (EEARH and EEARL)

Set EERE to 1

Get data from EEDR

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How to initialize EEPROM Use .ESEG before .DB .CSEG is used for code memory

Example .ESEG

.ORG $10

DATA1: DB $95 ; EEPROM memory in address $10

DATA2: DB $19 ; EEPROM memory in address $11

Example DATA1: DB $10 ; Code memory .ESEG

DATA2: DB $20 ; EEPROM memory

DATA3: DB $35 ; EEPROM memory

.CSEG

DATA4: DB $45 ; Code memory

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MACRO


What is MACRO A group of instructions that is used repeatedly Using MACRO we can write just one copy and invoke it everywhere

needed MACRO reduces code writing Increases the readability of code

Definition .MACRO name

……

.…..

.ENDMACRO

Parameters Can take up to 10 parameters @0 to @9 refer to parameters in the body of MACRO

MACRO


Example of MACRO definition .MACRO LOADIO

LDI R20, @1

OUT @0, R20

.ENDMACRO

Example of MACRO call LOADIO PORTA, 0x20

LOADIO SPL, 0x55

.EQU VAL_1=0xFF

LOADIO DDRC, VAL_1

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Switches on Input Ports


Pin should be defined input

DDRX.n 0

Case1: Internal pull-up is connected

PORTX.n 1

Case-2: Internal pull-up is not connected

PORTX.n 0

External pull-up should be connected

Current is 0.5mA on switch close

Good for all cases

Both give a logic 0 on switch close

Input Pin

Internal Pull-up

Push-Button

Input Pin

External Pull-up

Push-Button

Vcc=+5V

10K

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Switches on Input Ports


DIP switches usually have 8 switches Both, case-1 and case-2 from previous page is allowed Sequence of instructions to read is:

P0P1P2P3P4P5P6P7

AVR Input Port

SW-DIP8

Vcc=+5V

10K ResPack

P0P1P2P3P4P5P6P7

AVR Input Port

SW-DIP8

LDI R16, 0

OUT DDRX, R16 ;Define port as Input

LDI R16, 0xFF

OUT PORTX, R16 ;Internal Pull-up

IN R20, PINX ;Read Data from Pins

LDI R16, 0

OUT DDRX, R16 ;Define port as Input

LDI R16, 0

OUT PORTX, R16 ;No Internal Pull-up

IN R20, PINX ;Read Data from Pins

Bouncing Problem


Contact:

Push-button switches

Toggle switches

Electromechanical relays

Make and break Contact normally open switch

The effect is called "contact bounce" or, in a switch, "switch bounce”.

If used as edge-triggered input (as INT0), several interrupt is accorded

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Bouncing Problem


Hardware Solution

An RC time constant

larger than the switch bounce

Another hardware Solution

Vcc

R

C

OUT

Bouncing Problem


Software Solution

Periodically check

With appropriate time difference (10-20 ms) between check

Wait-and-see technique

When the input drops

An “appropriate” delay is executed (10-20 ms)

Then the value of the line is checked again to make sure the line has stopped bouncing

Read the new state of switch N time

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Interfacing a Keypad


16 keys arranged as a 4X4 matrix

If there is no controllable internal pull-up (general case)

Check to see if key pressed Define R as output port Define C as input port Place a 0000 on R Read port C If there is a 0 bit on C then Key has been pressed

Which key is being pressed Define R as output port Define C as input port For i=1 to 4 do

Place a 0 on Ri Read port C If there is a 0 on Cj then Keyij has been pressed Else, try next row

0 1 2 3

5 6 7

D E F

9 A B

C

8

4

C1C2

C3

C4

R1

R2

R3

R4

Output

Input

General uP based system



16 keys arranged as a 4X4 matrix

If there is internal pull-up (AVRs)

Both functions are combined

Define C as input port Enable internal pull-up of C Define R as output port Place a 0000 on R Read port C If C=1111 return(null) Else if there is a 0 on Cj then {

Define R as input port Enable internal pull-up of R Define C as output port Place a 0000 on C Read port R If there is a 0 on Ri then return(Keyij) }

0 1 2 3

5 6 7

D E F

9 A B

C

8

4

C1 C2 C3

C4

R1

R2

R3

R4 Outp

ut

Input

Input

Outp

ut

1 2

2

1

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.org 0 LDI R16, 0XFF ;define port D as output OUT DDRD, R16 WAIT_FOR_KEY: LDI R16,0XF0 ;define rows as input and column as output OUT DDRC,R16 LDI R16,0X0F ;pull up rows OUT PORTC,R16 ;and out 0 to columns lines IN R16, PINC ;read rows lines ORI R16, 0XF0 ;clear higher nibble to 1 CPI R16, 0XFF ;if no key pressed go back to up BREQ WAIT_FOR_KEY MOV R17,R16 ;save low nibble of pressed key to R16 LDI R16,0X00 ;set portc IO regs to initial values (0) OUT DDRC,R16 OUT PORTC,R16 LDI R16,0X0F ;define columns as input OUT DDRC,R16 ; and rows as output LDI R16,0XF0 ;pull up columns OUT PORTC,R16 ; and out 0 to rows lines IN R16, PINC ;read columns lines ORI R16, 0X0F AND R17, R16 ;combine low and high nibble of key code OUT PORTD, R17 ;out key code to port D WAIT2: IN R16, PINC ;read columns lines ORI R16, 0X0F CPI R16, 0XFF BRNE WAIT2 ;wait for release RJMP WAIT_FOR_KEY

The End

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Lecture note 7 AVR Advanced Assembly Language Programming Different Addressing Modes · 2015. 2....

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