Hi!
I have got a Japanese YIS-503II which is MSX1 but with V9938 VDP and i'm trying to make a small DOS untility to switch to 80 column mode. I have written very simple and small program but it kind of shows very strange behaviour and i'm stuck with it. The screen switches to 80 column but the coordinates shift in a weird way and then all characters (including cursor) appear on the screen twice, more like if screen is mirrored. I post the prog here and the photo of what it looks like - maybe someone knows what happens there?
org 100h
start:
xor a
ld (0FCB0H), a ; text screen is 0
rst 30h
db 00
; dw 005fh ; screen 0
dw 006Ch ; screen 0
ld a, 80
ld (0F3B0h), a ; LINLEN
ld (0F3AEh), a ; LINL40
ld hl, 0F3DFH ; RG0SAV
ld a, (hl)
or 4
ld (hl), a
ld b, a
ld c, 00
rst 30h
db 00
dw 0047h ; WRTVDP
ret
[img] http://msx.in.ua/z/80bug.jpg[/img]
Login or 등록 to post comments
