C64 Raster Interrupt

examples/c64/rasterirq.mfk

@@ -0,0 +1,48 @@
+
+void RasterA() {
+    vic_rasterirq_acknowledge()
+
+    // First raster split, set border to black
+    vic_border = black
+
+    // Set up next raster split
+    vic_rasterirq_reconfigure(RasterB.addr, $40)
+
+    vic_rasterirq_return()
+}
+
+void RasterB() {
+    vic_rasterirq_acknowledge()
+
+    // Second raster split, Dark grey
+    vic_border = dark_grey
+
+    // Set up next raster split
+    vic_rasterirq_reconfigure(RasterC.addr, $A0)
+
+    vic_rasterirq_return()
+}
+
+void RasterC() {
+    vic_rasterirq_acknowledge()
+
+    // Third raster split, Light grey
+    vic_border = light_grey
+
+    // Set up next raster split
+    vic_rasterirq_reconfigure(RasterA.addr, $00)
+
+    vic_rasterirq_return()
+}
+
+void main() {
+    byte i
+
+    // Configure Raster IRQ
+    vic_rasterirq_configure(RasterA.addr, $00)
+
+    // Loop forever
+    while true {
+        i = 0   // Do nothing here
+    }
+}

include/c64_vic.mfk

@@ -164,4 +164,44 @@ 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_rasterirq_return() {
+    lda #$00
+    jmp $EA81
+}