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Apple2: Setup IRQ/RST vectors in LC if needed

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Programs running under DOS3.3 need to setup correct
reset and IRQ vectors in the language card.
This commit is contained in:
Colin Leroy-Mira
2025-06-12 08:51:55 +02:00
committed by Oliver Schmidt
parent 2470851bfd
commit 990d65e4e4
4 changed files with 27 additions and 3 deletions
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24
libsrc/apple2/crt0.s
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@@ -58,6 +58,7 @@ init: ldx #zpspace-1
; Check for ProDOS.
ldy $BF00 ; MLI call entry point
cpy #$4C ; Is MLI present? (JMP opcode)
php ; Remember whether we're running ProDOS
bne basic
; Check the ProDOS system bit map.
@@ -99,7 +100,20 @@ basic: lda HIMEM
bit $C081
bit $C081
; Set the source start address.
plp ; Are we running ProDOS?
beq :+ ; Yes, no need to patch vectors
lda #<reset_6502
ldx #>reset_6502
sta ROM_RST
stx ROM_RST+1
lda #<irq_6502
ldx #>irq_6502
sta ROM_IRQ
stx ROM_IRQ+1
: ; Set the source start address.
; Aka __LC_LOAD__ iff segment LC exists.
lda #<(__ONCE_LOAD__ + __ONCE_SIZE__)
ldy #>(__ONCE_LOAD__ + __ONCE_SIZE__)
@@ -144,6 +158,14 @@ quit: jsr $BF00 ; MLI call entry point
.byte $65 ; Quit
.word q_param
reset_6502: ; Used with DOS3.3 programs
bit $C082 ; Switch in ROM
jmp (ROM_RST) ; Jump to ROM's RESET vector
irq_6502: ; Used with DOS3.3 programs
bit $C082 ; Switch in ROM
jmp (ROM_IRQ) ; Jump to ROM's IRQ/BRK vector
; ------------------------------------------------------------------------
.rodata