Table B-2. 8051 Instruction Set
Description
Instr.
Cycles
Hex
Code
Mnemonic
Byte
Arithmetic
ADD A, Rn
Add register to A
1
2
1
2
1
2
1
2
1
2
1
2
1
1
2
1
1
1
2
1
1
1
1
1
1
2
1
2
1
2
1
2
1
2
1
2
1
1
2
1
1
1
2
1
3
5
5
1
28-2F
25
ADD A, direct
ADD A, @Ri
ADDC A, #data
ADDC A, Rn
ADDC A, direct
ADDC A, @Ri
ADDC A, #data
SUBB A, Rn
SUBB A, direct
SUBB A, @Ri
SUBB A, #data
INC A
Add direct byte to A
Add data memory to A
Add immediate to A
26-27
24
Add register to A with carry
Add direct byte to A with carry
Add data memory to A with carry
Add immediate to A with carry
Subtract register from A with borrow
Subtract direct byte from A with borrow
Subtract data memory from A with borrow
Subtract immediate from A with borrow
increment A
38-3F
35
36-37
34
98-9F
95
96-97
94
04
INC Rn
Increment register
08-0F
05
INC direct
Increment direct byte
INC @ Ri
Increment data memory
Decrement A
06-07
14
DEC A
DEC Rn
Decrement Register
18-1F
15
DEC direct
DEC @Ri
Decrement direct byte
Decrement data memory
Increment data pointer
16-17
A3
INC DPTR
MUL AB
Multiply A by B
A4
DIV AB
Divide A by B
84
DA A
Decimal adjust A
D4
EZ-USB v1.9
Appendix B: 8051 Architectural Overview
B - 5
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