improved VIC II initialization

c64/kernal/init/e5a0.setup_vicii.s

@@ -1,22 +1,48 @@
 
 setup_vicii:
 
-	// XXX there is more to setup within this routine
+	// XXX it should also set default devices
 
-	// Set up default IO values (Compute's Mapping the 64 p215)
+	// Clear everything - turn off sprites (observed hanging around after
-	lda #$1B    // Enable text mode
+ 	// running programs and resetting), etc.
+
+	lda #$00
+ 	ldx #$2E
+ !:
+ 	sta __VIC_BASE, x
+ 	dex
+ 	bpl !-
+
+ 	// Disable C128 extra keys - just to be sure they won't interfere with anything
+
+ 	stx VIC_XSCAN
+
+ 	// Disable the C128 2MHz mode, it prevents VIC-II display from working correctly
+
+ 	stx VIC_CLKRATE
+
+	// Set up default IO values - Compute's Mapping the 64
+	// - page 129       - VIC_SCROLY
+	// - pages 140-144  - VIC_SCROLX
+	// - pages 145-146  - VIC_YMCSB
+
+	lda #$9B
 	sta VIC_SCROLY
-	lda #$C8    // 40 column etc
+	lda #$C8
-	sta VIC_SCROLX
+	sta VIC_SCROLX                     // 40 column etc
+	lda #$14
+	sta VIC_YMCSB
+	lda #$0F
+	sta VIC_IRQ                        // clear all interrupts
+
+
+	// XXX initialize $D012 (VIC_RASTER) - which values to use?
+
 
-	// Compute's Mapping the 64, p156
 	// We use a different colour scheme of white text on all blue
+
 	lda #$06
 	sta VIC_EXTCOL
 	sta VIC_BGCOL0
 
-	// Turn off sprites (observed hanging around after running programs and resetting)
-	lda #$00
-	sta VIC_SPENA
-
 	rts