mirror of
https://github.com/cc65/cc65.git
synced 2024-11-18 00:07:21 +00:00
66 lines
2.2 KiB
ArmAsm
66 lines
2.2 KiB
ArmAsm
;
|
|
; Oliver Schmidt, 07.09.2009
|
|
;
|
|
; unsigned __fastcall__ videomode (unsigned mode);
|
|
;
|
|
|
|
.export _videomode
|
|
.import COUT
|
|
|
|
.include "apple2.inc"
|
|
|
|
.segment "LOWCODE"
|
|
|
|
_videomode:
|
|
; Get and save current videomode flag
|
|
bit RD80VID
|
|
php
|
|
|
|
; If we are in 80 column mode then the 80 column firmware is
|
|
; known to be active so we can just print the ctrl-char code
|
|
; (even if this only means staying in the current videomode)
|
|
bpl :+
|
|
jsr COUT
|
|
bra done
|
|
|
|
; If we are in 40 column mode and want to set 40 column mode
|
|
; then we explicitly do nothing as we neither know about the
|
|
; current state of the 80 column firmware nor want to fix it
|
|
: cmp #$11 ; Ctrl-char code for 40 cols
|
|
beq done
|
|
|
|
; If we are in 40 column mode and want to set 80 column mode
|
|
; then we first presume the 80 column firmware being already
|
|
; active and print the ctrl-char code (this causes a garbage
|
|
; char to be printed on the screen if isn't already active)
|
|
jsr COUT
|
|
|
|
; If we successfully switched to 80 column mode then the 80
|
|
; column firmware was in fact already active and we're done
|
|
bit RD80VID
|
|
bmi done
|
|
|
|
; The 80 column firmware isn't already active so we need to
|
|
; initialize it - causing the screen to be cleared and thus
|
|
; the garbage char printed above to be erased (but for some
|
|
; reason the cursor horizontal position not to be zeroed)
|
|
stz CH
|
|
|
|
; Initializing the 80 column firmware needs the ROM switched
|
|
; in, otherwise it would copy the F8 ROM to the LC (@ $CEF4)
|
|
bit $C082
|
|
|
|
; Initialize 80 column firmware
|
|
jsr $C300 ; PR#3
|
|
|
|
; Switch in LC bank 2 for R/O
|
|
bit $C080
|
|
|
|
; Return ctrl-char code for setting previous
|
|
; videomode using the saved videomode flag
|
|
done: lda #$11 ; Ctrl-char code for 40 cols
|
|
plp
|
|
bpl :+
|
|
lda #$12 ; Ctrl-char code for 80 cols
|
|
: rts ; X was preserved all the way
|