A2osX/ProDOS.FX/ProDOS.S.IRQ.txt
2020-09-19 18:48:28 +02:00

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