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cc65/libsrc/cbm610/kirq.s
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101 lines
2.1 KiB
ArmAsm

;
; Ullrich von Bassewitz, 28.09.1998
;
; IRQ routine for the 610.
;
.export irq, nmi, k_irq, k_nmi
.import k_scnkey, k_udtim, k_rs232
.importzp tpi1
.include "zeropage.inc"
.include "io.inc"
.include "page3.inc"
; -------------------------------------------------------------------------
; This is the mapping of the active irq register of the 6525 (tpi1):
;
; Bit 7 6 5 4 3 2 1 0
; | | | | ^ 50 Hz
; | | | ^ SRQ IEEE 488
; | | ^ cia
; | ^ IRQB ext. Port
; ^ acia
; -------------------------------------------------------------------------
; IRQ entry point
.proc irq
pha
txa
pha
tya
pha
tsx
lda $104,x ; Get the flags from the stack
and #$10 ; Test break flag
bne L1
jmp (IRQVec)
L1: jmp (BRKVec)
.endproc
; -------------------------------------------------------------------------
; NMI entry point
.proc nmi
jmp (NMIVec)
.endproc
; -------------------------------------------------------------------------
; Kernal irq entry point. The IRQvec points here (usually).
k_irq:
lda IndReg ; Ind. Segment retten
pha
cld
lda #$0F
sta IndReg
ldy #tpiActIntReg
lda (tpi1),y ; Interrupt Register 6525
beq noirq
; -------------------------------------------------------------------------
; 50/60Hz interrupt
cmp #%00000001 ; ticker irq?
bne irq1
jsr k_scnkey ; Poll the keyboard
jsr k_udtim ; Bump the time
; -------------------------------------------------------------------------
; UART interrupt
irq1: cmp #%00010000 ; interrupt from uart?
bne irqend
jsr k_rs232 ; Read character from uart
; -------------------------------------------------------------------------
; Done
irqend: ldy #tpiActIntReg
sta (tpi1),y ; Clear interrupt
noirq: pla
sta IndReg
pla
tay
pla
tax
pla
k_nmi: rti