Comment by Narishma
> One of the random things burned into my memory for 6502 assembly is that LDA is $A9. I never separated the instruction from the register; it's not like they were general purpose.
You had LDA and LDX and LDY as separate instructions while the Z80 assembler had a single LD instruction with different operands. It's the same thing really.
Right, though the LD? and ST? instructions were kind of exceptions. You could only do arithmetic and stack and bitwise ops (and, or, eor, shift, rotate) with A, never X nor Y. Increment and decrement were X/Y only. You couldn't even add two registers together without stashing one in memory.