A2osX/ProDOS.203/ProDOS.S.IRQ.txt
2019-07-08 14:56:54 +02:00

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NEW
AUTO 3,1
* object code = mli_3
*
* this routine handles interrupts and is coded to reach 'lreset' precisely at
* address $FFCB (ROM rts opcode) for rom switching to function.
lanirq .EQ *-ofsR2
H2D9B pha $2D9B-2DFF moved to $FF9B-FFFF
lda accsav
sta oldacc
pla
sta accsav
pla get status register from stack
pha and put it back.
and #$10 is it a break or interrupt?
bne H2DC2 branch if break.
lda $D000 get ram bankid (LC1 = $D8, LC2=$EE)
eor #$D8 is the system active? ($D8)
beq sysactv branch if it is
lda #$FF
sysactv sta bankid
sta afbank
lda #>aftirq setup return address
pha
lda #<aftirq
pha
lda #$04 status reg with interrupt flag set
pha
H2DC2 lda #>romirq setup ROM re-entry
pha
lda #<romirq
pha
gorom .EQ *-ofsR2
sta romin hits ROM rts at $FFCB
* 'lreset' address must = $FFCB for rom switch i/o to work
lreset .EQ *-ofsR2
lda rreset+1
pha
lda rreset
pha
jmp gorom
rreset .EQ *-ofsR2
dc I2'resetv-1' rts to resetv
fix45 .EQ *-ofsR2
sta p8areg A register savearea
lda oldacc
sta accsav
lda ramin read/write RAM bank 1
lda ramin
lda afbank
jmp irqxit0
stypfx .EQ *-ofsR2 fix appletalk PFI bug
sty newpfxptr
sty preflag prefix flag
rts
stapfx .EQ *-ofsR2
sta newpfxptr
sta preflag
rts
* these 3 vectors hard-coded into processor
.DA nmivect' nmi handler
.DA lreset' reset handler
irqv .EQ *-ofsR2
dc i2'lanirq' irq handler
* end of obj mli_3
*--------------------------------------
MAN
SAVE USR/SRC/PRODOS.203/PRODOS.S.IRQ
LOAD USR/SRC/PRODOS.203/PRODOS.S
ASM