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julie_m · 9th Jul 2019, 8:03 am

Spot the schoolgirl error:

Code:

.dotest
LDY offsets,X
LDA (fxb),Y
INX
LDY offsets,X
CMP (mvb),Y
PHP \ save C,N,Z flags
INX \ will trash comparison result
PLP \ restore real result
RTS

In case you need context, it's called from a routine doing a bunch of comparisons on arrays of bytes starting at the addresses in fxb, fxb+1 and mvb, mvb+1; and it's doing them out-of-order. Hence the table of offsets indexed by X.

9th Jul 2019, 8:03 am	#22
julie_m Dekatron Join Date: May 2008 Location: Derby, UK. Posts: 7,735	Re: Fun with 6502 Assembler Spot the schoolgirl error: Code: .dotest LDY offsets,X LDA (fxb),Y INX LDY offsets,X CMP (mvb),Y PHP \ save C,N,Z flags INX \ will trash comparison result PLP \ restore real result RTS In case you need context, it's called from a routine doing a bunch of comparisons on arrays of bytes starting at the addresses in fxb, fxb+1 and mvb, mvb+1; and it's doing them out-of-order. Hence the table of offsets indexed by X. __________________ If I have seen further than others, it is because I was standing on a pile of failed experiments.