tweaking checkmem stuff

1 files changed, 14 insertions, 7 deletions

diff --git a/checkmem.s b/checkmem.s
index 90d21db..a87bbd2 100644
--- a/checkmem.s
+++ b/checkmem.s
@@ -1,7 +1,10 @@
 
 ; initial load segment for taipan. intended to be a tiny (1-sector)
-; routine that checks for the presence of BASIC or a cartridge, and
-; aborts the load if found.
+; routine that checks for the presence of BASIC or a cartridge, and aborts
+; the load if found. Also, it resets RAMTOP to RAMSIZ and does a GRAPHICS
+; 0, to avoid problems with funky loaders leaving the graphics screen
+; in the wrong place (Atarimax flash cart leaves it at $9cxx) or in the
+; wrong graphics mode (Fenders 3-sector loader doesn't set up GR.0).
 
 ; cl65 -o checkmem.xex -t none checkmem.s
 
@@ -15,8 +18,12 @@ start = $0600 ; use page 6 for now
 
  .org start
 
+; message is "Need 48K, remove cartridge" in screen codes.
 msg:
- .incbin "cartmsg.dat"
+ .byte $2e, $65, $65, $64, $00, $14, $18, $2b
+ .byte $0c, $00, $72, $65, $6d, $6f, $76, $65
+ .byte $00, $63, $61, $72, $74, $72, $69, $64
+ .byte $67, $65
 msglen = * - msg - 1
 
 S: .byte "S:",0
@@ -48,11 +55,11 @@ init:
  plp
  bcc have_cart
 
- ; if ramtop is $c000 or higher, we're OK, just exit.
+ ; if RAM size is $c000 or higher, we're OK, just exit.
  rts
 
 have_cart:
- ; if ramtop is below $c000, we have a cartridge (or XL BASIC).
+ ; if RAM size is below $c000, we have a cartridge (or XL BASIC).
  ; print the "remove cart" message...
  lda #<msg
  sta FR0
@@ -66,10 +73,10 @@ msgloop:
  dey
  bpl msgloop
 
+ sty CH ; y == $ff at this point, clear keyboard
  ; ...wait for a keystroke...
 wait4key:
- lda CH
- cmp #$ff
+ cpy CH
  beq wait4key
 
  ; ...and do a warmstart.