8051 Chap3 Instruction

7/29/2019 8051 Chap3 Instruction

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H Bch Khoa TP.HCM L Ch Thngwww.tinyurl.com/thongchile

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Chapter 3

Instruction Set

The 8051 Microcontroller

L Ch Thng

Ref. I. Scott Mackenzie, The 8051 Microcontroller

Instruction Set

255 instructions, mnemonic code

1-3 byte instructions

Opcode(operation code) + 0,1,2 bytes

address, data 1-byte instructions 139

2-byte instructions 92

3-byte instructions 24

2Ref. I. Scott Mackenzie L Ch Thng


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2

FIGURE B1 Opcode map

Jump, call, push, pop MOV


Coding format

Opcode (operation code) + operands

Operands addressing modes

Register

Direct : address

IndirectImmediate : constant

Relative : jump, branch, call (change PC)

Long : call

Indexed : array (base+offset)



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FIGURE 31 8051 Addressing modes. (a) Register addressing (b) Direct addressing (c) Indirect addressing (d)Immediate addressing (e) Relative addressing (f) Absolute addressing (g) Long addressing (h) Indexed addressing

Coding format

- Addressing modes


Register Addressing

Addressing Modes



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4

Register bankso Bank 0 (default), Bank 1, Bank 2, and Bank 3

o Change register bank by selecting bits RS1 and RS0 the

program status word (discussed next slide)

o One bank includes 8 registers: R0 through R7

Ex:

Read the contents of location 05H

into the accumulator

MOV A, R5

orMOV A, 05H

Write the contents of the accumulator

into location 00H

MOV R0, A


Program Status Word (PSW)



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5

Register Addressing

- 8 registers: R0 ~ R7

Ex: MOV A,R6

ADD A,R7

- 4 banks of registers: Bank 0 (default), Bank 1, Bank 2, and Bank 3

- The active bank is determined by bit PSW.3 & PSW.4 (reviewed inthe next 2 slides)

Ex: MOV PSW,#00011000B; activates bank 3

Ex: INC DPTR

Addressing Modes


Direct Addressing

Addressing Modes



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6

Bit-addressable

RAM

(20H-2FH)

Register banks

(00H-1FH) DPTR

Using for MUL,DIV

Internal (on-chip) data memory:

General purpose

RAM

(30H-7FH)

Special function

registers

(80H-FFH)11Ref. I. Scott Mackenzie L Ch Thng

Direct Addressing

- Access internal memory

Ex: MOV A,30H

ADD A,31H

- Access special function registers: can use the mnemonicabbreviation instead of the addresses

Ex: MOV P1,A; Accumulator Port 1

MOV 90H,A; same

Opcode: F5 90

Ex: MOV R1,ACC

MOV R1,0E0H

MOV R1,A

Same function, but

Addressing Modes

0000 A9E0 1 MOV R1,ACC0002 A9E0 2 MOV R1,0E0H0004 F9 3 MOV R1,A 12Ref. I. Scott Mackenzie L Ch Thng


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Immediate Addressing

- Source operand is constant

- Use # sign

Ex: MOV A,#12

MOV A,#0CH

MOV R1,#0

ADD A,#11110001B

MOV DPTR,#2000H

Addressing Modes


Indirect Addressing

- Address of a memory location is stored in R0 or R1

- Use @sign to access the content of this memory location: @R0,@R1

Ex: MOV R0,#30H

MOV A,@R0

Ex: Implementation of array

MOV R0, #60H

LOOP: MOV @R0, #0

INC R0

CJNE R0, #80H, LOOP

Addressing Modes



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8

Relative Addressing

- Used with SJMP instruction.

- A relative address (or offset) is an 8-bit signed value.

- It is added to PC to form a new value for PC.

- Range: -128 ~ +127

- Usually used with label

Ex: SJMP LABEL1 is in memory at locations 0100H and 0101H

PC = 0102H

- LABEL1 is the label representing an instruction at location 0107H Relative offset is 0107H 0102H = 5

Opcode of SJMP LABEL1 is 80 05

Addressing Modes


Relative Addressing

Addressing Modes

FIGURE 32 Calculating the offset for relative addressing. (a) Short jump ahead inmemory (b) Short jump back in memory



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9

Absolute AddressingAddressing Modes

FIGURE 33 Instruction encoding for absolute addressing. (a) Memory map showing 2Kpages (b) Within any 2K page, the upper five address bits are the same for the source anddestination addresses. The lower 11 bits of the destination are supplied in the instruction


Long Addressing

- Used with LCALL and LJMP instruction

- Use full 16-bit address

- Usually used with label

Ex: LCALL SUBPROGRAM1

LJMP LABEL2

Indexed Addressing- Base address (PC or DPTR) + Offset (A) Effective Address

- Used with JMP or MOVC

Ex: MOVC A, @A+DPTR

JMP @A+DPTR

Addressing Modes



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Instruction Types

Data transfer

Arithmetic

Logical

Boolean variable

Program branching


8051 Instruction Set SummaryLegend



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8051 Instruction Set SummaryData Transfer





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Ex: Write a program to move (write) 40H to location 30H in internal

RAM using 2 methods of addressing: direct addressing and indirect

addressing.

Method 1: Direct addressing

ORG 0000H

MOV 30H,#40H

END

Method 2: Indirect addressing

ORG 0000HMOV R0,#30H

MOV @R0,#40H

END



Ex: Write a program to clear location 31H in internal RAM using 2

methods of addressing: direct addressing and indirect addressing.

Hint: to clear means to reset the data to zero.


ORG 0000H

MOV 31H,#0

ENDMethod 2: Indirect addressing

ORG 0000H

MOV R0,#31H

MOV @R0,#0

END



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Ex: Write a program to move (write) the content of A to location

32H in internal RAM using 2 methods of addressing: direct

addressing and indirect addressing.


ORG 0000H

MOV 32H,A

END



MOV @R0,A

END



Ex: Write a program to move the content of location 33H in internal

RAM to register A using 2 methods of addressing: direct addressing

and indirect addressing.


ORG 0000H

MOV A,33H


ORG 0000H

MOV R0,#33H

MOV A,@R0

END



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RAM to register A using 2 methods of addressing: direct addressing

and indirect addressing.


ORG 0000H

MOV A,33H

END



MOV A,@R0

END




RAM to location 35H in internal RAM using 2 methods of

addressing: direct addressing and indirect addressing.


ORG 0000H

MOV 35H,34H


ORG 0000H

MOV R0,#34H

MOV A,@R0

INC R0

MOV @R0,A

END28Ref. I. Scott Mackenzie L Ch Thng


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15


Ex: Write a program to write 40H to location 0030H in external

RAM.

ORG 0000H

MOV A,#40H

MOV DPTR,#0030H

MOVX @DPTR,A

END



Ex: Write a program to clear location 0031H in externalRAM.

ORG 0000H

CLR A

MOV DPTR,#0031H

MOVX @DPTTR,A

END



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Ex: Write a program to move the content of location 0032H in

externalRAM to register A.

ORG 0000H

MOV DPTR,#0032H

MOVX A,@DPTTR

END



Ex: Write a program to move the content of register A to location

0033H in externalRAM.

ORG 0000H

MOV DPTR,#0033H

MOVX @DPTTR,A

END



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Ex: Write a program to move the content of location 0034H in

externalRAM to location 0035H in externalRAM.

ORG 0000H

MOV DPTR,#0034H

MOVX A,@DPTTR

INC DPTR

MOVX @DPTR,A

END


8051 Instruction Set SummaryArithmetic Operations



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8051 Instruction Set SummaryFlag Effect


8051 Instruction Set SummaryLogic Operations



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8051 Instruction Set SummaryBoolean Variable


8051 Instruction Set SummaryProgram Branching



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8051 Instruction Set SummaryProgram Branching


ArithmeticStatus in PSW : CY (carry/borrow), PSW.7

OV (overflow), PSW.2

AC (Auxiliary carry), PSW.6

Flag 0 (zero), PSW.5

P (Even parity), PSW.0

RS1,0 PSW.4,3CY for unsigned integer

OV for signed integer, (+)+(+)(-), (-)+(-)(+)

ADDC, SUBB multi-byte operations

DA (decimal adjustment) for BCD



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Examples allowed addressing mode for specifiedinstructions

; ADD/SUB with C/B

MOV A, R7

CLR C ; bit operation, used bit-address

SUBB A, R6

; inc/dec data in data memory

MOV A, direct

INC A

MOV direct, A

; 2-byte data dec

DEC DPL

MOV R7, DPL

CJNE R7, #0FFH, SKIP;compare and jump if

DEC DPH

SKIP: .


; MUL/DIV

MUL AB

DIV AB ;PSW status of A

SUBB A, R6

; BCD addition

MOV A, 43H

ADD A, 41H

DA A

MOV 41H, A

MOV A, 42H

ADD A, 40H

DA A

MOV 40H, A



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LogicANL, ORL, XRL

CLR A, CPL A (complement)

RL, RLC

RR, RRC

SWAP

MOV R7, #8

LOOP: RLC A

XCH A, 0F0H ; register B : 0F0HRRC A

XCH A, 0F0H

DJNZ R7, LOOP; dec/jump, R7- counter

XCH A, 0F0H


Data transferMOV (internal memory), MOVX (external memory)

XCH A,

XCHD A, ; exchange digits (lower nibble)

PUSH, POP

PUSH : sp++; @sp data

POP : Ri@sp ; sp--;sp (stack pointer) : 08H-7FH

if sp>7FH; no operation



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; LOOK-UP TABLE, TRICKED; usually PC can

; not be accessed directly

MOV A, #ENTRY_NUMBER; n+size (RET)

CALL LOOK_UP

.

; subroutine

LOOK_UP:

MOVC A, @A+PC ; move constant

RET

TABLE:; define byte-data (array for high-level language)

DB data1, data2, data3,


Time-space consideration

; TABLE LOOKUP - 13 bytes, 5 clocks

SQUARE:

INC A ; sizeof (RET), 1 clocks

MOVC A, @A+PC ; move constant, 2 clocks

RET ; 2 clocks

TABLE:

; define data (array for high-level language

DB 0,1,4,9,16, 25, 36, 49, 64, 81

; Use multiplication - 8 bytes, 13 clocks

SQUARE:

PUSH 0F0H ; register B ,LABEL, 2 clocks

MOV 0F0H, A ; 1 clocks

MUL AB ; 4 cycles

POP 0F0H ; 2 clocks

RET ; 2 clocks



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BooleanBit operand, address 0-127

SETB

CLR

MOV ,

CLR C (single instruction) compare with CLR CY

JC LABEL (jump if CY=1)

JB , LABEL (jump if bit==1)

JBC , LABEL (jump if bit==1 and clear bit)

JNC LABELJNB , LABEL


FIGURE 34 Simple implementation of a logic AND operation



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FIGURE 35 Instruction sequence for worst-case propagation delay

LOOP:

MOV C, P1.0

ANL C, P1.1

MOV P1.2,C

SJMP LOOP

; XOR

MOV C, BIT1JNB BIT2, SKIP

CPL C

SKIP:

..


Program branchingSJMP : 8-bit offset

LJMP : 11-bit address (2KB segment)

AJMP : 16-bit

LCALL, ACALL

ExampleMOV DPTR, #JMP_TABLE

MOV A, #INDEX_NUMBER

RL A ; index*2-byte

JMP @A+DPTR



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Example :

; DJNZ : Dec and jump non-zero

; use as counter

MOV R7, #10

LOOP:

DJNZ R7, LOOP

; CJNZ : compare and jump non-zero

CJNZ A, #03H, SKIP ; 03H : control-CSJMP TERMINATE

SKIP:


Example : bit-wise XOR

XRB:

MOV 20H, C

ANL C, /P

MOV 21H, C

MOV C, P

ANL C,/20H

ORL C,21H

Other ways

(1) Use byte-wise XOR

(2) Use JB, JNB



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FIGURE 38 Interface to a DIP switch and 7-segment LED

Example : BCD to 7-segment decoder


Some Simple Instructions

MOV dest,source ; dest = source

MOV A,#72H ;A=72H

MOV R4,#62H ;R4=62H

MOV B,0F9H ;B=the content of F9th byte of RAM

MOV DPTR,#7634H

MOV DPL,#34H

MOV DPH,#76H

MOV P1,A ;mov A to port 1

Note 1:MOV A,#72H MOV A,72H

After instruction MOV A,72H the content of 72th byte of RAM willreplace in Accumulator.

Note 2:MOV A,R3 MOV A,3

Ref. I. Scott Mackenzie 56L Ch Thng


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ADD A, Source ;A=A+SOURCE

ADDA,#6 ;A=A+6

ADDA,R6 ;A=A+R6

ADD A,6 ;A=A+[6] or A=A+R6

ADD A,0F3H ;A=A+[0F3H]

SUBB A, Source ;A=A-SOURCE-C

SUBB A,#6 ;A=A-6

SUBB A,R6 ;A=A+R6


MUL & DIV

MUL AB ;B|A = A*B

MOV A,#25H

MOV B,#65H

MUL AB ;25H*65H=0E99;B=0EH, A=99H

DIV AB ;A = A/B, B = A mod B

MOV A,#25

MOV B,#10

DIV AB ;A=2, B=5Ref. I. Scott Mackenzie 58L Ch Thng


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SETB bit ; bit=1CLR bit ; bit=0

SETB C ; CY=1

SETB P0.0 ;bit 0 from port 0 =1

SETB P3.7 ;bit 7 from port 3 =1

SETB ACC.2 ;bit 2 from ACCUMULATOR =1

SETB 05 ;set high D5 of RAM loc. 20h

Note:

CLR instruction is similar to SETB

i.e.:

CLR C ;CY=0

But following instruction is only for CLR:

CLR A ;A=0


DEC byte ;byte=byte-1

INC byte ;byte=byte+1

INC R7

DEC A

DEC 40H ; [40]=[40]-1



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RR RL RRC RLC A

EXAMPLE:

RR A

RR:

RRC:

RL:

RLC:

C

C


ANL - ORL XRL

Bitwise Logical Operations:

AND, OR, XOREXAMPLE:

MOV R5,#89H

ANLR5,#08H

CPL A ;1s complementExample:

MOV A,#55H ;A=01010101 B

L01: CPL A

MOV P1,A

ACALL DELAY

SJMP L01



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Stack in the 8051 The register used to

access the stack iscalled SP (stackpointer) register.

The stack pointer inthe 8051 is only 8 bitswide, which meansthat it can take value

00 to FFH. When 8051powered up, the SPregister contains value07.

7FH

30H

2FH

20H

1FH

17H

10H

0FH

07H

08H

18H

00HRegister Bank 0

(Stack) Register Bank 1

Register Bank 2

Register Bank 3

Bit-Addressable RAM

Scratch pad RAM


Example:

MOV R6,#25H

MOV R1,#12H

MOV R4,#0F3H

PUSH 6

PUSH 1

PUSH 4

0BH

0AH

09H

08H

Start SP=07H

25

0BH

0AH

09H

08H

SP=08H

F3

12

25

0BH

0AH

09H

08H

SP=08H

12

25

0BH

0AH

09H

08H

SP=09H



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LOOP and JUMP Instructions

JZ Jump if A=0

JNZ Jump if A/=0

DJNZ Decrement and jump if A/=0

CJNE A,byte Jump if A/=byte

CJNE reg,#data Jump if byte/=#data

JC Jump if CY=1

JNC Jump if CY=0

JB Jump if bit=1

JNB Jump if bit=0

JBC Jump if bit=1 and clear bit

Conditional Jumps :


DJNZ:

Write a program to clear ACC, then

add 3 to the accumulator ten time

Solution:

MOV A,#0

MOV R2,#10AGAIN: ADD A,#03

DJNZ R2,AGAIN ;repeat until R2=0 (10 times)

MOV R5,A



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LJMP(long jump)LJMP is an unconditional jump. It is a 3-byte instruction. Itallows a jump to any memory location from 0000 to FFFFH.

AJMP(absolute jump)

In this 2-byte instruction, It allows a jump to any memorylocation within the 2k block of program memory.

SJMP(short jump)

In this 2-byte instruction. The relative address range of 00-

FFH is divided into forward and backward jumps, that is ,within -128 to +127 bytes of memory relative to the address ofthe current PC.


CALL Instructions

Another control transfer instruction is the CALL instruction,

which is used to call a subroutine.

LCALL(long call)

This 3-byte instruction can be used to call subroutineslocated anywhere within the 64K byte address space

of the 8051.

ACALL (absolute call)

ACALL is 2-byte instruction. the target addressof the subroutine must be within 2K byte range.



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Example:

Write a program to copy a block of 10 bytes from RAMlocation starting at 37h to RAM location starting at 59h.

Solution:

MOV R0,#37h ; source pointer

MOV R1,#59h ; dest pointer

MOV R2,#10 ; counter

L1: MOV A,@R0

MOV @R1,AINC R0

INC R1

DJNZ R2,L1


Performing the Addition with 8051

. 65536's 256's 1's

. R6 R7

+ R4 R5

= R1 R2 R3

1.Add the low bytes R7 and R5, leave the answer in R3.

2.Add the high bytes R6 and R4, adding any carry from step 1, and leave the answer in R2.

3.Put any carry from step 2 in the final byte, R1.



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Steps 1, 2, 3MOV A,R7 ;Move the low-byte into the accumulator

ADD A,R5 ;Add the second low-byte to the accumulator

MOV R3,A ;Move the answer to the low-byte of the result

MOV A,R6 ;Move the high-byte into the accumulator

ADDC A,R4 ;Add the second high-byte to the accumulator, plus carry.

MOV R2,A ;Move the answer to the high-byte of the result

MOV A,#00h ;By default, the highest byte will be zero.

ADDC A,#00h ;Add zero, plus carry from step 2.

MOV R1,A ;Move the answer to the highest byte of the resultRef. I. Scott Mackenzie 71L Ch Thng

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References

L Ch Thng

I. Scott Mackenzie, The 8051 Microcontroller

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