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Reject setting screen at $0000 due to overlap with zeropage and kernal vars.

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This commit is contained in:
mc78 2024-08-26 10:25:02 +02:00
parent a914be0fdc
commit 1aeb3aeb13
1 changed files with 3 additions and 2 deletions
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5
libsrc/cbm/workingscreenaddr.s
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@ -11,6 +11,7 @@
_cbm_set_working_screen:
tax
beq @error ; Reject setting screen at zero page location
and #3
bne @error
cpx #$10 ; Screen addr must not be set to $1000-$1fff nor $9000-$9fff
@ -33,6 +34,6 @@ _cbm_set_working_screen:
tax
rts
@error:
lda #$ff
tax
lda #$01
ldx #$00
rts