base:use_shy_as_sty_x_or_shx_as_stx_y
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base:use_shy_as_sty_x_or_shx_as_stx_y [2017-11-17 09:15] – cruzer | base:use_shy_as_sty_x_or_shx_as_stx_y [2017-11-17 21:48] (current) – cruzer | ||
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However, there' | However, there' | ||
- | The opcodes are classified as unstable, but this only affects the and' | + | ===== Instabilities ===== |
+ | |||
+ | The opcodes are classified as unstable, but this only affects | ||
+ | |||
+ | The first instability is that the and' | ||
+ | |||
+ | Another instability comes when you cross a page boundary like this: | ||
+ | |||
+ | < | ||
+ | ldy #$14 | ||
+ | ldx #$01 | ||
+ | shy $0eff,x | ||
+ | </ | ||
+ | |||
+ | Normally you would expect the value to end up in $0f00, but for reasons unknown, the page changes to the value stored ((H + 1) & y), which in this case is ($0e + 1) & $14 = $04. So the value ends up in $0400. | ||
base/use_shy_as_sty_x_or_shx_as_stx_y.txt · Last modified: 2017-11-17 21:48 by cruzer