preparation for up-scrollable console

src/kernal/screen_m65/mega65_scrmodeset.s

@@ -56,21 +56,50 @@ m65_scrmodeset_internal: // entry point for M65_MODE65
 	ldx #$00
 	stx VIC_CHARSTEP+1
 	
-	// Set the base screen addresses:
-	// - in VIC_SCRNPTR and M65_SCRTXTBASE to $16000
-	// - in VIC_COLPTR to $0000
+	// Set the following locations:
+	// - M64_SCRWINMODE                - for scroll-console mode
+	// - M65_SCRSEG, VIC_SCRNPTR+2/+3  - for screen in $0001xxxx area
 
+	stx M64_SCRWINMODE                           // .X = 0
+	stx M65_SCRSEG+1                             
+	stx VIC_SCRNPTR+3
+	inx
+	stx M65_SCRSEG+0	
+	stx VIC_SCRNPTR+2
+
+	// Set the following locations:
+	// - M65_SCRBASE                   - for screen starting from $xxxx6000
+	// - M65_SCRVIEW, VIC_SCRNPTR+0/+1 - for screen viewport starting from the same address
+	// - M65_COLVIEW, VIC_COLPTR       - for using color memory from the start
+
+	ldx #$60
+	stx M65_SCRBASE+1
+	stx M65_SCRVIEW+1
+	stx VIC_SCRNPTR+1
+
+	ldx #$00
+	stx M65_SCRBASE+0
+	stx M65_SCRVIEW+0
+	stx VIC_SCRNPTR+0
+
+	stx M65_COLVIEW+0
+	stx M65_COLVIEW+1
 	stx VIC_COLPTR+0
 	stx VIC_COLPTR+1
-	stx VIC_SCRNPTR+0
-	stx M65_SCRTXTBASE+0
-	stx VIC_SCRNPTR+3
-	stx M65_SCRTXTBASE+3
-	inx
-	stx VIC_SCRNPTR+2
-	stx M65_SCRTXTBASE+2
-	ldx #$60
-	stx VIC_SCRNPTR+1
-	stx M65_SCRTXTBASE+1
+
+	// Set the following locations:
+	// - M65_SCREND                    - for max 200 lines of virtual screen
+	// - M65_SCRVIEWMAX                - as above, but depending on the mode
+
+	ldx #$80
+	stx M65_SCRGUARD+0
+	ldx #$9E
+	stx M65_SCRGUARD+1
+
+	ldx M65_SCRMODE
+	lda m65_scrtab_viewmax_lo, x
+	sta M65_SCRVIEWMAX+0
+	lda m65_scrtab_viewmax_hi, x
+	sta M65_SCRVIEWMAX+1
 
 	rts