oldrom.asm

   1         SECTION "a",HOME
   2
   3 main:
   4         ld a, $FF       ; Note that we are alive.
   5         ld [$FF51],a
   6
   7         ld sp, $DFF0
   8
   9         ld hl, $DF81
  10         ld a, $80
  11         ld [hl], a
  12
  13         ld c, $07
  14         ld a, $04       ;start timer, 4.096KHz
  15         ld [c], a
  16 ;diqs:  ei
  17 ;       ld a, $80
  18 ;       ld c, $51
  19 ;       ld [c], a
  20 ;       jr diqs
  21         call irqhand
  22         ei
  23 coqs: jr coqs
  24
  25         section "Diq", HOME[$38]
  26 fuqed:
  27         di
  28         jr fuqed
  29
  30         section "fuq",HOME[$100]
  31 irqhand:
  32         PUSH AF
  33         PUSH BC
  34         PUSH DE
  35         PUSH HL
  36
  37         xor a
  38         ld c, $0F       ; ack the irq
  39         ld [c], a
  40
  41         ld a, $41       ; print A
  42         call putc
  43
  44         ld hl, $DF81
  45         inc [hl]
  46         ld a, [hl]
  47         ld c, $51
  48         ld [c], a
  49
  50
  51         POP HL
  52         POP DE
  53         POP BC
  54         POP AF
  55         RETI
  56         db $18,$FE,$18,$FE,$18,$FE,$18,$FE,$18,$FE,$18,$FE,$18,$FE,$18,$FE
  57         db $18,$FE,$18,$FE,$18,$FE,$18,$FE,$18,$FE,$18,$FE,$18,$FE,$18,$FE
  58         db $18,$FE,$18,$FE,$18,$FE,$18,$FE,$18,$FE,$18,$FE,$18,$FE,$18,$FE
  59
  60 putc:
  61         ld b, 0
  62         ld c, $50
  63         push af
  64 .waitport:
  65         ld a,[c]
  66         cp b
  67         jr nz,.waitport
  68         pop af
  69         ld [c],a
  70         ret