MCS-51 MCU assembly language: What are the data transfer instructions?

Data transfer instructions are the most frequently used instructions in MCS-51 microcontroller assembly language programming, including data transfer between internal RAM, registers, external RAM and program memory.

Data transfer operation refers to transferring data from a source address to a destination address without changing the content of the source address.

1. Instructions with accumulator A as the destination operand

MOV   A,   ＃data    ； A← ＃data

MOV   A,   Rn       ； n=0~7， A← (Rn)

MOV A, @Ri; i=0.1, A← ((Ri))

MOV A, direct; A← (Rn) direct is the internal RAM or SFR address

2. Instructions with Rn as the destination operand

MOV    Rn，  A       ；Rn ← (A) ，  n=0~7

MOV    Rn ， direct    ；Rn ← (direct) 

MOV    Rn ，＃data    ；Rn ← ＃data

3. Instructions with direct addresses as destination operands

MOV   direct,  A        ；direct← (A)

MOV   direct,  Rn       ； direct← (Rn) ，       n=0~7

MOV   direct,  @Ri      ； direct← (( Ri ) ) ， i=0,1

MOV   direct,  direct     ；direct← (direct)

MOV   direct,  #data      ；direct← ＃data

4. Instructions with register indirect addresses as destination operands

MOV @Ri, A ; ((Ri) )← (A) ,i=0.1

MOV   @Ri ， direct    ； ((Ri) )← (direct)

MOV   @Ri ，＃data    ； ((Ri) )← ＃data

Byte swap instructions

XCH A , Rn ； (A) ← →(Ri)

XCH A , direct ； (A) ← →(direct)

XCH  A ,  @Ri     ； (A) ← →(Ri)

Nibble swap instruction

XCHD A, @Ri ；(A)0-3 ← →((Ri )) 0-3

Accumulator A and external data transfer instructions

MOVX A, @DPTR; A← ((DPTR)) address range 64K

MOVX A, @Ri ； A← ((Ri)) Address range 0～255

MOVX @DPTR, A ； (DPTR) ←(A)

MOVX    @Ri ,  A    ； (Ri) ←(A)

Table Lookup Instructions

1）MOVC A, @A+DPTR ； A ←((A)+(DPTR))

2）MOVC  A,   @A+PC   ； A ←((A)+(pc))