mirror of https://github.com/cc65/cc65.git
92 lines
2.4 KiB
ArmAsm
92 lines
2.4 KiB
ArmAsm
;
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; Oliver Schmidt, 2012-11-17
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;
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; IRQ handling (Apple2 version)
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;
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.export initirq, doneirq
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.import callirq, __dos_type, _exit
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.include "apple2.inc"
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.macpack apple2
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.segment "ONCE"
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initirq:
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; Check for ProDOS
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lda __dos_type
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beq prterr
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; Allocate interrupt vector table entry
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jsr $BF00 ; MLI call entry point
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.byte $40 ; Alloc interrupt
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.addr i_param
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bcs prterr
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; Enable interrupts, as old ProDOS versions (i.e. 1.1.1)
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; jump to SYS and BIN programs with interrupts disabled.
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cli
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rts
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; Print error message and exit
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prterr: ldx #msglen-1
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: lda errmsg,x
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jsr $FDED ; COUT
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dex
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bpl :-
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jmp _exit
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errmsg: .ifdef __APPLE2ENH__
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scrcode $0D, "tpurretni colla ot deliaF", $0D
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.else
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scrcode $0D, "TPURRETNI COLLA OT DELIAF", $0D
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.endif
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msglen = * - errmsg
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.code
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doneirq:
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; Check for valid interrupt vector table entry number which
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; IS necessary as this gets called even if initirq failed.
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lda int_num
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beq :+
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; Deallocate interrupt vector table entry
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dec i_param ; Adjust parameter count
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jsr $BF00 ; MLI call entry point
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.byte $41 ; Dealloc interrupt
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.addr i_param
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: rts
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.segment "LOWCODE"
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intptr:
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; ProDOS TechRefMan, chapter 6.2:
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; "Each installed routine must begin with a CLD instruction."
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cld
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; Call interruptors and check for success
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jsr callirq
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bcc :+
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; ProDOS TechRefMan, chapter 6.2:
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; "When the routine that can process the interrupt is called, it
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; should ... return (via an RTS) with the carry flag clear."
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clc
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rts
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; ProDOS TechRefMan, chapter 6.2:
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; "When a routine that cannot process the interrupt is called,
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; it should return (via an RTS) with the cary flag set ..."
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: sec
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rts
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.data
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; MLI parameter list for (de)alloc interrupt
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i_param:.byte $02 ; param_count
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int_num:.byte $00 ; int_num
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.addr intptr ; int_code
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