implemented 'GO' BASIC command, started work on native MEGA65 mode

src/kernal/board_m65/mega65_jumptable.s

@@ -0,0 +1,129 @@
+// #LAYOUT# M65 KERNAL_0 #TAKE
+// #LAYOUT# *   *        #IGNORE
+
+//
+// Not this is not an official Kernal API extension (yet)! It is subject to change!
+//
+
+
+M65_JMODE64:
+
+	// Disable interrupts, they might interfere
+
+	sei
+
+	// XXX provide full implementation
+
+	// Set the magic string to mark legacy mode
+
+	lda #$00
+	sta M65_MAGICSTR+0
+	sta M65_MAGICSTR+1
+	sta M65_MAGICSTR+2
+
+	// Reenable interrupts
+
+	cli
+
+	// Switch CPU speed back to slow and quit
+
+	jmp M65_JSLOW
+
+
+
+M65_JMODE65:
+
+	// Disable interrupts, they might interfere
+
+	sei
+
+	// Swithc CPU speed to fast
+
+	jsr M65_JFAST
+
+	// 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
+
+	// XXX provide full implementation
+
+	// Switch VIC to VIC-IV mode
+
+	lda #$47
+	sta VIC_KEY
+	lda #$53
+	sta VIC_KEY
+
+	// XXX provide proper implementation
+
+	// Set screen mode to 80 columns
+
+	lda $D031
+	ora #$80
+	sta $D031
+
+	// Set screen RAM base to $15000
+
+	lda #$00
+	sta $D060
+	sta LDTB1+0
+	sta $D063
+	sta LDTB1+3
+	lda #$50
+	sta $D061
+	sta LDTB1+1
+	lda #$01
+	sta $D062
+	sta LDTB1+2
+
+	// Set something in screen memory
+
+	lda #$01
+
+	// STA [],Z
+	nop
+	.byte $92
+	.byte LDTB1
+
+!:
+	nop
+	jmp !-
+
+
+
+M65_JISMODE65: // checks if mode is native M65 one, BEQ = jump if native mode
+
+	pha
+
+	lda M65_MAGICSTR+0
+	cmp #$4D // 'M'
+	bne !+
+	lda M65_MAGICSTR+1
+	cmp #$36 // '6'
+	bne !+
+	lda M65_MAGICSTR+2
+	cmp #$35 // '5'
+!:
+	pla
+	rts
+
+
+
+
+M65_JSLOW: // set CPU speed to 1 MHz
+
+	lda #$40
+	skip_2_bytes_trash_nvz
+
+	// FALLTROUGH
+
+M65_JFAST: // set CPU speed to 40 MHz
+
+	lda #$41
+	sta CPU_D6510
+	rts