ASEMBBLY OPERATION & SINTAX PROGRAM MCS51

ARITHMETIC OPERATIONS

Mnemonic	Description	Bytes Cycles
ADD A,Rn	Add register to A	1	1
ADD A,	direct Add direct byte to A	2	1
ADD A,	@Ri Add indirect Ram to A	1	1
ADD A,#data	Add immediate data to A	2	1
ADDC A,Rn	Add register to A with Carry	1	1
ADDC A,direct	Add direct byte to A with Carry	2	1
ADDC A,@Ri	Add indirect RAM to A with Carry	1	1
ADDC A,#data	Add immediate data to A with Carry	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 A	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 A	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
MUL AB	Multiply A & B (A x B => BA)	1	4
DIV AB	Divide A by B (A/B => A + B)	1	4
DA A	Decimal Adjust A	1	1

LOGICAL OPERATIONS

Mnemonic	Description	Bytes Cycles
ANL A,Rn	AND register to A	1	1
ANL A,direct	AND direct byte to A	2	1
ANL A,@Ri	AND indirect RAM to A	1	1
ANL A,#data	AND immediate data to A	2	1
ANL direct,A	AND A to direct byte	2	1
ANL direct,#data	AND immediate data to direct byte	3	2
ORL A,Rn	OR register to A	1	1
ORL A,direct	OR direct byte to A	2	1
ORL A,@Ri	OR indirect RAM to A	1	1
ORL A,#data	OR immediate data to A	2	1
ORL direct,A	OR A to direct byte	2	1
ORL direct,#data	OR immediate data to direct byte	3	2
XRL A,Rn	Exclusive-OR register to A	1	1
XRL A,direct	Exclusive-OR direct byte to A	2	1
XRL A,@Ri	Exclusive-OR indirect RAM to A	1	1
XRL A,#data	Exclusive-OR immediate data to A	2	1
XRL direct,A	Exclusive-OR A to direct byte	2	1
XRL direct,#data	Exclusive-OR immediate data to direct byte	3	2
CLR A	Clear A	1	1
CPL A	Complement A	1	1
RL A	Rotate A Left	1	1
RLC A	Rotate A Left through Carry	1	1
RR A	Rotate A Right	1	1
RRC A	Rotate A Right through Carry	1	1
SWAP A	Swap nibbles within A	1	1

DATA TRANSFER

Mnemonic	Description	Bytes Cycles
MOV A,Rn	Move register to A	1	1
MOV A,direct	Move direct byte to A	2	1
MOV A,@Ri	Move indirect RAM to A	1	1
MOV A,#data	Move immediate data to A	2	1
MOV Rn,A	Move A 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 A 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 A 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 16-bit constant	2	1
MOVC A,@A+DPTR	Move Code byte relative to DPTR to A	1	2
MOVC A,@A+PC	Move Code byte relative to PC to A	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 A	1	1
XCH A,direct	Exchange direct byte with A	2	1
XCH A,@Ri	Exchange indirect RAM with A	1	1
XCHD A,@Ri	Exchange low-order Digit indirect RAM with A	1	1

BOOLEAN VARIABLE MANIPULATION

Mnemonic	Description	Bytes Cycles
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 flag	2	2
ORL C,bit	OR direct bit to Carry flag	2	2
ORL C,/bit	OR complement of direct bit to Carry flag	2	2
MOV C,bit	Move direct bit to Carry flag	2	1
MOV bit,C	Move Carry flag to direct bit	2	2

PROGRAM AND MACHINE CONTROL

Mnemonic	Description	Bytes Cycles
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 DPTR	1	2
JZ rel	Jump if A is Zero	2	2
JNZ rel	Jump if A is Not Zero	2	2
JC rel	Jump if Carry flag is set	2	2
JNC rel	Jump if No Carry flag	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
JBC bit,rel	Jump if direct Bit is set & Clear bit	3	2
CJNE A,direct,rel	Compare direct to A & Jump if Not Equal	3	2
CJNE A,#data,rel	Compare immediate to A & Jump if Not Equal	3	2
CJNE Rn,#data,rel	Compare immed. to reg. & Jump if Not Equal	3	2
CJNE @Ri,#data,rel	Compare immed. to ind. & Jump if Not Equal	3	2
DJNZ Rn,rel	Decrement register & Jump if Not Zero	2	2
DJNZ direct,rel	Decrement direct byte & Jump if Not Zero	3	2
NOP	No operation	1	1

Notes on data addressing modes
Rn         Working register R0-R7
direct     128 internal RAM locations, any I/O port, control or status register
@Ri      Indirect internal RAM location addressed by register R0 or R1
#data     8-bit constant included in instruction
#data16 16-bit constant included in instruction
bit 128    software flags, any I/O pin, control or status bit

Notes on program addressing modes
addr16  Destination address may be anywhere in 64-kByte program address space
addr11  Destination address will be within same 2-kByte page of program address space as first byte of the following instruction
rel  8-bit  offset relative to first byte of following instruction (+127, -128)

All mnemonics copyrighted © Intel Corporation 1979
Information from Intel Application Note AP-69