hi, I bet there is a standard way, or best way to do this, so how would you span pages in an indexed offset,

like $C000, x

then moving through the MSB as well as the LSB

$C100, X
$C200, x
$C300, x

ect...

maby if I just store the MSB in one address and the LSB in another, then can some how load them, hmm

any help is appreciated thanks

I believe that mode is called Absolute,X. I'm not really sure what you're trying to do, but usually if you need to span multiple pages of memory, you'd use the indirect indexed addressing mode ($xx),Y.

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Be whatever the situation demands.

Yeah.... Indirect,Y looks like what you want to go with.

Just write your destination address to somewhere in zero page memory (like $10):

LDA #$00
STA $10
LDA #$C0
STA $11


Then you can use Indirect,Y with Y as the low byte of the address. When Y wraps to zero, just increment $11 and you'll do the next page.

so in zero page using indirect indexed

say $00 is = $00
and $01 is = $c0

and the ldy with say #$05

so if lda $00,y is instructed
then the accumulator would actually load the value in address $C000 ? or $C005 ?

does y actually offset the LSB value, or does it overwrite the LSB

so like does

say $00 is = $10
and $01 is = $c0

and the ldy with say #$05

lda $00, y

still equate to lda $C005 or is it now $C015

thanks

> so if lda $00,y is instructed

It would actyally be LDA ($00),Y (can't forget the parenthesis, without them, you're using zero page mode).

Anyway, in that example, A would be loaded with what's at $C005. The value of Y is added to the adress at $00 (which was $C000). If Y + the LSB is greater than $FF.. the page boundary WILL be crossed as expected (at the cost of 1 more CPU cycle).

So in your bottom example... it would be reading from $C015. But again... don't forget the parenthesis.


"LDA ($00),Y" is not the same as "LDA $00,Y"

yes, I left out the parenthesis, another mistake there, thanks for the nfos/help