rom4x/rom5x/B0_CFF9_switch_cmd.s
2017-03-11 00:19:40 -08:00

16 lines
519 B
ArmAsm

; This is the dispatch routine to call the primary ROM 5X
; functions of intercepting RESET and the boot process.
; If one enters at $CFF9, the command $A9 is loaded and
; we go to the BELL1 hijack. If entering at $CFFA, we
; load the command $EA and proceed the same way.
; thus we get two dispatch codes in 6 bytes.
#include "iic+.defs"
.text
* = $cff9 ; 7 bytes available here, but don't count on $CFFF
lda #$a9 ; lda opcode
nop ; jmp/jsr $cffa does lda #$ea
jmp $fbdf ; jump to bell1 hijack
; total 6 bytes.