C64 VIC-II RasterIRQ methods and example

examples/c64/rasterirq.mfk

@@ -0,0 +1,40 @@
+
+void RasterA()
+{
+	vic_rasterirq_acknowledge()
+	vic_border = $00
+
+    vic_rasterirq_reconfigure(RasterB.addr, $40)
+	vic_raster_return()
+}
+
+void RasterB()
+{
+	vic_rasterirq_acknowledge()
+	vic_border = $04
+
+    vic_rasterirq_reconfigure(RasterC.addr, $A0)
+	vic_raster_return()
+}
+
+void RasterC()
+{
+	vic_rasterirq_acknowledge()
+	vic_border = $02
+
+    vic_rasterirq_reconfigure(RasterA.addr, $00)
+	vic_raster_return()
+}
+
+void main() 
+{
+    byte i
+
+    // Configure Raster IRQ
+    vic_rasterirq_configure(RasterA.addr, $00)
+
+	while true
+	{
+        i = 0
+	}
+}

include/c64_vic.mfk

@@ -164,4 +164,48 @@ const byte medium_gray = 12
 const byte light_green = 13
 const byte light_blue = 14
 const byte light_grey = 15
-const byte light_gray = 15
+const byte light_gray = 15
+
+
+asm void vic_rasterirq_configure(pointer CallbackFunction, byte RasterLine)
+{
+    sei
+    ldx CallbackFunction.lo
+    stx $0314
+    ldy CallbackFunction.hi
+    sty $0315
+    lda #$7f                    ;CIA interrupt off
+    sta $dc0d
+    lda #$01                    ;Raster interrupt on
+    sta $d01a
+    lda #27                     ;High bit of interrupt position = 0
+    sta $d011
+    lda RasterLine              ;Line where next IRQ happens
+    sta $d012
+    lda $dc0d                   ;Acknowledge IRQ (to be sure)
+    cli
+    rts
+}
+
+asm void vic_rasterirq_reconfigure(pointer CallbackFunction, byte RasterLine)
+{
+    ldx CallbackFunction.lo
+    stx $0314
+    ldy CallbackFunction.hi
+    sty $0315
+    lda RasterLine              ;Line where next IRQ happens
+    sta $d012
+    rts
+}
+
+asm macro void vic_rasterirq_acknowledge()
+{
+    lda #$FF
+    sta $D019
+}
+
+asm macro void vic_raster_return()
+{
+    lda #$00
+    jmp $EA81
+}