mirror of
https://github.com/a2-4am/4cade.git
synced 2024-06-01 23:41:39 +00:00
36 lines
1.1 KiB
Plaintext
36 lines
1.1 KiB
Plaintext
|
;license:MIT
|
||
|
|
;(c) 2020 by qkumba
|
||
|
|
;
|
||
|
|
; Functions to enable and disable VBL polling on various
|
||
|
|
; Apple II models
|
||
|
|
|
||
|
|
iWaitForVBL
|
||
|
|
sei ; IIc is special
|
||
|
|
sta $C07F ; enable access to VBL register
|
||
|
|
sta $C05B ; enable VBL polling
|
||
|
|
sta $C07E ; disable access to VBL register
|
||
|
|
WaitForVBL_iie ; IIe/IIgs have a relatively sane VBL
|
||
|
|
; but it's reversed between the two
|
||
|
|
; so we default to IIe, and patch in
|
||
|
|
; the reverse case if it's a IIGS.
|
||
|
|
- bit $C019
|
||
|
|
patch_VBL_iigs1
|
||
|
|
bpl -
|
||
|
|
patch_VBL_iic
|
||
|
|
- lda $C019 ; $c019 bit 7 is sticky, reset it (SMC->#$70 for IIc)
|
||
|
|
patch_VBL_iigs2
|
||
|
|
bmi -
|
||
|
|
WaitForVBL_nop ; II/II+ have no easy VBL
|
||
|
|
rts
|
||
|
|
|
||
|
|
iUnwaitForVBL
|
||
|
|
rts ; SMC on IIc
|
||
|
|
- bit $C019
|
||
|
|
bpl -
|
||
|
|
lda $C070 ; $c019 bit 7 is sticky, reset it
|
||
|
|
sta $C07F ; enable access to VBL register
|
||
|
|
sta $C05A ; disable VBL polling
|
||
|
|
sta $C07E ; disable access to VBL register
|
||
|
|
cli
|
||
|
|
rts
|