various cleanups

src/kernal/extapi_m65/mega65_modeset.s

@@ -0,0 +1,71 @@
+// #LAYOUT# M65 KERNAL_1 #TAKE
+// #LAYOUT# *   *        #IGNORE
+
+
+M65_MODESET:
+
+	// Carry clear = set native mode; Carry set = set legacy mode 
+
+	bcc m65_mode65
+
+	// FALLTROUGH
+
+m65_mode64:
+
+	// Disable interrupts, they might interfere
+
+	sei
+
+	// Set the magic string to mark legacy mode
+
+	lda #$00
+	sta M65_MAGICSTR+0
+	sta M65_MAGICSTR+1
+	sta M65_MAGICSTR+2
+
+	// Restore VIC-II configuration
+
+	jsr viciv_shutdown
+	jsr vicii_init
+
+	// Reenable interrupts
+
+	cli
+
+	// Switch CPU speed back to slow and quit
+
+	jmp M65_SLOW
+
+
+m65_mode65:
+
+	// Disable interrupts, they might interfere
+
+	sei
+
+	// Switch CPU speed to fast
+
+	jsr M65_FAST
+
+	// Set the magic string to mark native mode
+
+	lda #$4D // 'M'
+	sta M65_MAGICSTR+0
+	lda #$36 // '6'
+	sta M65_MAGICSTR+1
+	lda #$35 // '5'
+	sta M65_MAGICSTR+2
+
+	// Initialize VIC-IV
+
+	jsr vicii_init
+	jsr viciv_init
+
+	// Set screen mode to 80x50
+
+	lda #$02
+	jsr m65_scrmodeset_internal
+
+	// Clear the screen
+
+	jmp M65_CLRSCR