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https://github.com/A2osX/A2osX.git
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86 lines
1.7 KiB
Plaintext
86 lines
1.7 KiB
Plaintext
NEW
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AUTO 3,1
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*--------------------------------------
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* this routine handles interrupts and is coded to reach 'lreset' precisely at
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* address $FFCB (ROM rts opcode) for rom switching to function.
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* $2D9B-2DFF moved to $FF9B-FFFF
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*--------------------------------------
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IRQ.START
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XDOS.IRQV ldx #$FA save 6 bytes of page 0
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.2 lda $00,x
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sta svzerop-$FA,x
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inx
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bne .2
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ldx #0
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.3 stx irqXindex
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lda inttbl+1,x test for a valid routine.
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beq .4 branch if no routine.
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jsr gointX execute
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bcc irqdone
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.4 ldx irqXindex
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inx
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inx
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cpx #10
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bne .3
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inc irqcount allow 255 unclaimed interrupts
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bne irqdone before system death.
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lda #$01 bad irq so
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jsr sysdeath kill the system.
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.LIST ON
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IRQ.FREE1 .EQ $ffc8-*
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.LIST OFF
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.BS IRQ.FREE1
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gorom sta RROMBNK2 hits ROM rts at $FFCB
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* 'lreset' address must = $FFCB for rom switch i/o to work
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lreset lda /resetv-1
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pha
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lda #resetv-1
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pha
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jmp gorom
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irqdone ldx #$FA
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.1 lda svzerop-$FA,x restore the zero page
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sta $00,x
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inx
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bne .1
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rti
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gointX jmp (inttbl,x) interrupt routine x
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irqcount .HS 00 # of unclaimed interrupts.
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irqXindex .HS 00
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svzerop .HS 000000000000
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.LIST ON
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IRQ.FREE2 .EQ $fffa-*
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.LIST OFF
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.BS IRQ.FREE2
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.DA nmivect nmi handler
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.DA lreset reset handler
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irqv .DA * PATCHED with ROM vector by LDR
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.LIST OFF
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*--------------------------------------
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IRQ.LEN .EQ *-IRQ.START
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MAN
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SAVE USR/SRC/PRODOS.FX/PRODOS.S.IRQ
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LOAD USR/SRC/PRODOS.FX/PRODOS.S
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ASM
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