8085 assembly instructions MOV, LDA and STA

assembly copy mov 8085
Lu Ka picture Lu Ka · Nov 24, 2016 · Viewed 10.7k times · Source

I get the point of MOV, STA and LDA instructions, but what I don't understand is why are there three different instructions for two different processes?

  • STA is for copying data from accumulator to memory location,
  • LDA is for copying data from memory location to accumulator and
  • MOV is for copying data between registers plus registers and memory.

So, what I can do with STA and LDA instructions can be done with MOV instruction too, right?

Answer

Weather Vane picture Weather Vane · Nov 24, 2016

The instructions LDA and STA move data between memory and A. The instruction MOV either moves data between registers, or between a register and a memory location specified by HL.

LDA and STA are used when the address can be resolved at assembly/link time.

MOV is used when the memory address is computed at run time, and is placed in HL. For example, when you are iterating through an array.

You have discovered direct and indirect memory addressing.

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