get CIA IRQ running.

c64/kernal/ioinit.s

@@ -14,5 +14,26 @@ ioinit:
 	sta $D020
 	lda #$06
 	sta $D021
+
+	;; Enable CIA1 IRQ and ~50Hz timer
+	;; (https://csdb.dk/forums/?roomid=11&topicid=69037)
+	lda #$7f
+	sta $DC0D 		; First disable all
+
+	;; Set timer interval to ~1/50th of a second
+	lda #<20000
+	sta $dc04
+	lda #>20000
+	sta $dc05
+
+	;; Enable timer interrupt
+	lda #$81
+	sta $dc0d
+
+	;; Enable timer A to run continuously
+	;; (http://codebase64.org/doku.php?id=base:timerinterrupts)
+	lda #$11
+	sta $dc0e
+	lda $dc0d
 	
 	rts

c64/kernal/irq_handler.s

@@ -14,6 +14,9 @@ irq_handler:
 	tya
 	pha
 
+	;; Acknowledge CIA interrupt
+	lda $dc0d
+	
 	;; Call interrupt routine
 	;; (but only if initialised)
 	lda $0314