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cc65/libsrc/cx16/videomode.s

47 lines
1.1 KiB
ArmAsm

;
; 2022-03-28, Greg King
;
; /* Video mode defines */
; #define VIDEOMODE_80x60 0x00
; #define VIDEOMODE_80x30 0x01
; #define VIDEOMODE_40x60 0x02
; #define VIDEOMODE_40x30 0x03
; #define VIDEOMODE_40x15 0x04
; #define VIDEOMODE_20x30 0x05
; #define VIDEOMODE_20x15 0x06
; #define VIDEOMODE_320x240 0x80
; #define VIDEOMODE_SWAP (-1)
;
; signed char __fastcall__ videomode (signed char Mode);
; /* Set the video mode, return the old mode.
; ** Return -1 if Mode isn't valid.
; ** Call with one of the VIDEOMODE_xx constants.
; */
;
.export _videomode
.import SCREEN_MODE
.proc _videomode
sec ; Get old mode
pha
jsr SCREEN_MODE
plx
pha ; Save old mode
txa
clc ; Set new mode
jsr SCREEN_MODE
pla ; Get back old mode
ldx #>$0000 ; Clear high byte
bcc @L1
; The new mode is invalid. Return -1.
dex
txa
@L1: rts
.endproc