2 ; Ullrich von Bassewitz, 27.09.1998
4 ; void set_brk (unsigned Addr);
5 ; void reset_brk (void);
8 .export _set_brk, _reset_brk
10 .export _brk_a, _brk_x, _brk_y, _brk_sr, _brk_pc
11 .import BRKStub, BRKOld, BRKInd
25 uservec: jmp $FFFF ; Patched at runtime
30 ; Set the break vector
34 stx uservec+2 ; Set the user vector
37 ora BRKOld+2 ; Did we save the vector already?
38 bne @L1 ; Jump if we installed the handler already
40 lda BRKVec ; Save the old vector
45 lda #<BRKStub ; Set the break vector to our stub
50 lda #<brk_handler ; Set the indirect vector to our handler
60 ; Reset the break vector
65 beq @L9 ; Jump if vector not installed
69 sta BRKOld+1 ; Clear the saved vector
77 ; Break handler, called if a break occurs
88 and #$EF ; Clear break bit
92 sbc #2 ; Point to start of brk
98 jsr uservec ; Call the user's routine