Can't figure out post-indexed indirect addressing

[raydempsey]

LDA #$FF
STA $E704

LDA #$04
STA $A0
LDA #$E7
STA $A1

LDY #$00
LDA ($A0),Y
STA $A2

I am hoping that $00A2 will have a value of FF but it is not happening. What am I doing wrong?

-Ray

[thefox]

I am hoping that $00A2 will have a value of FF but it is not happening. What am I doing wrong?

Looks correct, except that if you're coding for NES, $E704 is probably ROM and the first write of $FF has no effect.

[za909]

You're loading a value from $E704, which is part of the cartridge space, so it'll only happen if there's the $FF as a constant at $E704

Code: Select all

.org $E704

  .db $FF

I don't know which assembler you're using, so you might have to change the .db to .byte