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cc65/libsrc/apple2/irq.s

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;
; Oliver Schmidt, 2012-11-17
;
; IRQ handling (Apple2 version)
;
.export initirq, doneirq
.import callirq, __dos_type, _exit
.include "apple2.inc"
.segment "INIT"
initirq:
; Check for ProDOS
lda __dos_type
beq prterr
; Allocate interrupt vector table entry
jsr $BF00 ; MLI call entry point
.byte $40 ; Alloc interrupt
.addr i_param
bcs prterr
rts
; Print error message and exit
prterr: ldx #msglen-1
: lda errmsg,x
jsr $FDED ; COUT
dex
bpl :-
jmp _exit
errmsg: .ifdef __APPLE2ENH__
.byte $8D, 't'|$80, 'p'|$80, 'u'|$80, 'r'|$80, 'r'|$80
.byte 'e'|$80, 't'|$80, 'n'|$80, 'i'|$80, ' '|$80, 'c'|$80
.byte 'o'|$80, 'l'|$80, 'l'|$80, 'a'|$80, ' '|$80, 'o'|$80
.byte 't'|$80, ' '|$80, 'd'|$80, 'e'|$80, 'l'|$80, 'i'|$80
.byte 'a'|$80, 'F'|$80, $8D
.else
.byte $8D, 'T'|$80, 'P'|$80, 'U'|$80, 'R'|$80, 'R'|$80
.byte 'E'|$80, 'T'|$80, 'N'|$80, 'I'|$80, ' '|$80, 'C'|$80
.byte 'O'|$80, 'L'|$80, 'L'|$80, 'A'|$80, ' '|$80, 'O'|$80
.byte 'T'|$80, ' '|$80, 'D'|$80, 'E'|$80, 'L'|$80, 'I'|$80
.byte 'A'|$80, 'F'|$80, $8D
.endif
msglen = * - errmsg
.code
doneirq:
; Check for valid interrupt vector table entry number which
; IS necessary as this gets called even if initirq failed.
lda int_num
beq :+
; Deallocate interrupt vector table entry
dec i_param ; Adjust parameter count
jsr $BF00 ; MLI call entry point
.byte $41 ; Dealloc interrupt
.addr i_param
: rts
.segment "LOWCODE"
intptr:
; ProDOS TechRefMan, chapter 6.2:
; "Each installed routine must begin with a CLD instruction."
cld
; Call interruptors and check for success
jsr callirq
bcc :+
; ProDOS TechRefMan, chapter 6.2:
; "When the routine that can process the interrupt is called, it
; should ... return (via an RTS) with the carry flag clear."
clc
rts
; ProDOS TechRefMan, chapter 6.2:
; "When a routine that cannot process the interrupt is called,
; it should return (via an RTS) with the cary flag set ..."
: sec
rts
.data
; MLI parameter list for (de)alloc interrupt
i_param:.byte $02 ; param_count
int_num:.byte $00 ; int_num
.addr intptr ; int_code