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