4cade/src/prelaunch/aztec.a

;license:MIT
;(c) 2019-2020 by qkumba

!cpu 6502
!to "build/PRELAUNCH/AZTEC",plain
*=$106

    !source "src/prelaunch/common.a"

         +ENABLE_ACCEL
         lda   #$60
         sta   $A00
         jsr   $800       ; find and load "DOS"
         lda   #<callback
         sta   $B748
         lda   #>callback
         sta   $B749
         jmp   $B700

keypress
         lda   $C000
         bpl   keypress
         cmp   #$8D
         bne   keypress
         lda   #$8D
         rts

intercept
         jsr   $BD5F
         jsr   $BD09
         lda   $656B
         cmp   #$2C
         clc
         bne   +
         lda   #$20
         sta   $656B
         lda   #<keypress
         sta   $656C
         lda   #>keypress
         sta   $656D
+        rts

callback
         ldx   #0
         stx   $9E52
         inx
         stx   $9E53      ; reset vector patch
         lda   #$4C
         sta   $BD06
         lda   #<intercept
         sta   $BD07
         lda   #>intercept
         sta   $BD08
         sta   $656B

         +DISABLE_ACCEL
         jmp   $9D84

!if * > $1C0 {
  !error "code is too large, ends at ", *
}