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MOVing between two memory addresses

Asked 2009-08-19T10:46:00.370
33

I'm trying to learn assembly (so bear with me) and I'm getting a compile error on this line:

mov byte [t_last], [t_cur]

The error is

error: invalid combination of opcode and operands

I suspect that the cause of this error is simply that its not possible for a mov instruction to move between two memory addresses, but half an hour of googling and I haven't been able to confirm this - is this the case?

Also, assuming I'm right that means I need to use a register as an intermediate point for copying memory:

mov cl, [t_cur]
mov [t_last], cl

Whats the recommended register to use (or should I use the stack instead)?

assembly x86 instructions mov
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2 Answers

7

It's really simple in 16 bit, just do the following:

     push     di
     push     si
     push     cx
     mov      cx,(number of bytes to move)
     lea      di,(destination address)
     lea      si,(source address)
     rep      movsb
     pop      cx
     pop      si
     pop      di

Note: the pushes & pops are neceessary if you need to save the contents of the registers.

answered 2012-07-10T00:49:39.440
4

There's also a MOVS command from moving data from memory to memory:

MOV SI, OFFSET variable1
MOV DI, OFFSET variable2
MOVS
answered 2009-08-19T11:01:15.643

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