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| -rw-r--r-- | memsetup.asm | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/memsetup.asm b/memsetup.asm index fa81ae6..de9c7d9 100644 --- a/memsetup.asm +++ b/memsetup.asm @@ -1,3 +1,14 @@ +; Initial load segment for the fnchat.exe executable. Sets MEMTOP and +; RAMTOP to $6A00, disables BASIC (on XL/XE), disables ANTIC DMA, then +; returns so the rest of the .xex continues to load. + +; This is pretty weird: when loading fnchat.xex from MyDOS 4.50 or +; (apparently) Spartados X, a 0 byte gets written to our display +; list. It's up in the $BFxx area, which is to say, where the GR.0 +; screen used by DOS lives... and somehow these DOSes are writing a +; 0 byte to the screen (a space) in the middle of loading the file. +; Setting SAVMSC to something else ($0600, here) avoids this. + *= $2000 memsetup lda $d301 ; PORTB @@ -9,6 +20,9 @@ memsetup lda #0 sta $02e5 ; MEMTOP low sta $022f ; SDMCTL (turn off screen) + sta $58 ; SAVMSC + lda #$06 + sta $59 ; SAVMSC+1 lda $14 ; RTCLOK+2 loop cmp $14 ; wait until next frame |