Implementation of the layers in VERA is working now in text mode!

Added a number of new methods in conio to accommodate this.

screenlayer()
setscreenlayermapbase()
getscreenlayermapbase()
screenlayerenable()
screenlayerdisable()
screenlayerenabled()

src/main/fragment/cache/fragment-cache-wdc65c02.asm

@@ -1497,3 +1497,697 @@ cpy #0
 bne {la1}
 //FRAGMENT vbuyy=_dec_vbuyy
 dey
+//FRAGMENT pbuz1=qbuc1_derefidx_vbuz2
+ldy {z2}
+lda {c1},y
+sta {z1}
+lda {c1}+1,y
+sta {z1}+1
+//FRAGMENT vbuz1=pbuc1_derefidx_vbuz2
+ldy {z2}
+lda {c1},y
+sta {z1}
+//FRAGMENT vbuz1_ge_vbuz2_then_la1
+lda {z1}
+cmp {z2}
+bcs {la1}
+//FRAGMENT vbuz1=vbuz1_minus_vbuz2
+lda {z1}
+sec
+sbc {z2}
+sta {z1}
+//FRAGMENT pbuz1=qbuc1_derefidx_vbuaa
+tay
+lda {c1},y
+sta {z1}
+lda {c1}+1,y
+sta {z1}+1
+//FRAGMENT pbuz1=qbuc1_derefidx_vbuxx
+lda {c1},x
+sta {z1}
+lda {c1}+1,x
+sta {z1}+1
+//FRAGMENT pbuz1=qbuc1_derefidx_vbuyy
+lda {c1},y
+sta {z1}
+lda {c1}+1,y
+sta {z1}+1
+//FRAGMENT vbuaa=pbuc1_derefidx_vbuz1
+ldy {z1}
+lda {c1},y
+//FRAGMENT vbuxx=pbuc1_derefidx_vbuz1
+ldy {z1}
+ldx {c1},y
+//FRAGMENT vbuyy=pbuc1_derefidx_vbuz1
+ldx {z1}
+ldy {c1},x
+//FRAGMENT vbuz1=pbuc1_derefidx_vbuaa
+tay
+lda {c1},y
+sta {z1}
+//FRAGMENT vbuaa=pbuc1_derefidx_vbuaa
+tay
+lda {c1},y
+//FRAGMENT vbuxx=pbuc1_derefidx_vbuaa
+tay
+ldx {c1},y
+//FRAGMENT vbuyy=pbuc1_derefidx_vbuaa
+tax
+ldy {c1},x
+//FRAGMENT vbuz1=pbuc1_derefidx_vbuxx
+lda {c1},x
+sta {z1}
+//FRAGMENT vbuaa_ge_vbuz1_then_la1
+cmp {z1}
+bcs {la1}
+//FRAGMENT vbuxx=vbuxx_minus_vbuz1
+txa
+sec
+sbc {z1}
+tax
+//FRAGMENT vbuz1=vbuz1_minus_vbuaa
+eor #$ff
+sec
+adc {z1}
+sta {z1}
+//FRAGMENT vbuxx=vbuxx_minus_vbuaa
+sta $ff
+txa
+sec
+sbc $ff
+tax
+//FRAGMENT vbuz1=vbuz1_minus_vbuxx
+txa
+eor #$ff
+sec
+adc {z1}
+sta {z1}
+//FRAGMENT vbuxx=vbuxx_minus_vbuxx
+lda #0
+tax
+//FRAGMENT vbuz1=vbuz1_minus_vbuyy
+tya
+eor #$ff
+sec
+adc {z1}
+sta {z1}
+//FRAGMENT vbuxx=vbuxx_minus_vbuyy
+txa
+sty $ff
+sec
+sbc $ff
+tax
+//FRAGMENT vbuxx_ge_vbuz1_then_la1
+cpx {z1}
+bcs {la1}
+//FRAGMENT vbuz1_ge_vbuxx_then_la1
+lda {z1}
+stx $ff
+cmp $ff
+bcs {la1}
+//FRAGMENT vbuz1_ge_vbuyy_then_la1
+lda {z1}
+sty $ff
+cmp $ff
+bcs {la1}
+//FRAGMENT vbuxx_ge_vbuyy_then_la1
+sty $ff
+cpx $ff
+bcs  {la1}
+//FRAGMENT vbuaa=vbuxx
+txa
+//FRAGMENT vbuyy=vbuxx
+txa
+tay
+//FRAGMENT vbuyy_ge_vbuz1_then_la1
+cpy {z1}
+bcs {la1}
+//FRAGMENT 0_eq_vbuyy_then_la1
+cpy #0
+beq {la1}
+//FRAGMENT vbuyy_lt_vbuc1_then_la1
+cpy #{c1}
+bcc {la1}
+//FRAGMENT vbuxx=vbuaa
+tax
+//FRAGMENT pbuz1=_deref_qbuc1
+lda {c1}
+sta {z1}
+lda {c1}+1
+sta {z1}+1
+//FRAGMENT pbuz1=_ptr_vbuz2
+lda {z2}
+sta {z1}
+lda #0
+sta {z1}+1
+//FRAGMENT vwuz1=vbuz2_plus_vwuc1
+lda {z2}
+clc
+adc #<{c1}
+sta {z1}
+lda #>{c1}
+adc #0
+sta {z1}+1
+//FRAGMENT pbuz1=pbuz2_plus_vwuz3
+lda {z2}
+clc
+adc {z3}
+sta {z1}
+lda {z2}+1
+adc {z3}+1
+sta {z1}+1
+//FRAGMENT pbuz1=_ptr_vbuaa
+sta {z1}
+lda #0
+sta {z1}+1
+//FRAGMENT pbuz1=_ptr_vbuxx
+stx {z1}
+ldx #0
+stx {z1}+1
+//FRAGMENT pbuz1=_ptr_vbuyy
+sty {z1}
+ldy #0
+sty {z1}+1
+//FRAGMENT pbuz1=pbuz2_plus_vwuz1
+lda {z1}
+clc
+adc {z2}
+sta {z1}
+lda {z1}+1
+adc {z2}+1
+sta {z1}+1
+//FRAGMENT pbuz1=pbuz1_plus_vbuaa
+clc
+adc {z1}
+sta {z1}
+bcc !+
+inc {z1}+1
+!:
+//FRAGMENT vwuz1=vbuaa
+sta {z1}
+lda #0
+sta {z1}+1
+//FRAGMENT vwuz1=vwuz2_rol_1
+lda {z2}
+asl
+sta {z1}
+lda {z2}+1
+rol
+sta {z1}+1
+//FRAGMENT vwuz1=vwuz1_rol_1
+asl {z1}
+rol {z1}+1
+//FRAGMENT _deref_pbuz1=vbuz2
+lda {z2}
+ldy #0
+sta ({z1}),y
+//FRAGMENT _deref_pbuz1=vbuxx
+txa
+ldy #0
+sta ({z1}),y
+//FRAGMENT _deref_pbuz1=vbuyy
+tya
+ldy #0
+sta ({z1}),y
+//FRAGMENT vbuaa=vbuyy
+tya
+//FRAGMENT vbuz1=vbuz2_rol_7
+lda {z2}
+asl
+asl
+asl
+asl
+asl
+asl
+asl
+sta {z1}
+//FRAGMENT vbuaa=vbuz1_rol_7
+lda {z1}
+asl
+asl
+asl
+asl
+asl
+asl
+asl
+//FRAGMENT vbuxx=vbuz1_rol_7
+lda {z1}
+asl
+asl
+asl
+asl
+asl
+asl
+asl
+tax
+//FRAGMENT vbuyy=vbuz1_rol_7
+lda {z1}
+asl
+asl
+asl
+asl
+asl
+asl
+asl
+tay
+//FRAGMENT vwuz1=_word__deref_pbuz2
+ldy #0
+lda ({z2}),y
+sta {z1}
+lda #0
+sta {z1}+1
+//FRAGMENT vwuz1=vwuz2_rol_5
+lda {z2}
+asl
+sta {z1}
+lda {z2}+1
+rol
+sta {z1}+1
+asl {z1}
+rol {z1}+1
+asl {z1}
+rol {z1}+1
+asl {z1}
+rol {z1}+1
+asl {z1}
+rol {z1}+1
+//FRAGMENT vwuz1=vwuz2_rol_4
+lda {z2}
+asl
+sta {z1}
+lda {z2}+1
+rol
+sta {z1}+1
+asl {z1}
+rol {z1}+1
+asl {z1}
+rol {z1}+1
+asl {z1}
+rol {z1}+1
+//FRAGMENT pwuz1=pwuc1
+lda #<{c1}
+sta {z1}
+lda #>{c1}
+sta {z1}+1
+//FRAGMENT vwuz1=pwuz2_derefidx_vbuz3
+ldy {z3}
+lda ({z2}),y
+sta {z1}
+iny
+lda ({z2}),y
+sta {z1}+1
+//FRAGMENT vbuaa_eq_vbuc1_then_la1
+cmp #{c1}
+beq {la1}
+//FRAGMENT vwuz1=pwuz2_derefidx_vbuaa
+tay
+lda ({z2}),y
+sta {z1}
+iny
+lda ({z2}),y
+sta {z1}+1
+//FRAGMENT vwuz1=pwuz2_derefidx_vbuxx
+txa
+tay
+lda ({z2}),y
+sta {z1}
+iny
+lda ({z2}),y
+sta {z1}+1
+//FRAGMENT vwuz1=pwuz2_derefidx_vbuyy
+lda ({z2}),y
+sta {z1}
+iny
+lda ({z2}),y
+sta {z1}+1
+//FRAGMENT vwuz1=_word__deref_pbuz1
+ldy #0
+lda ({z1}),y
+sta {z1}
+lda #0
+sta {z1}+1
+//FRAGMENT vwuz1=vwuz1_rol_4
+asl {z1}
+rol {z1}+1
+asl {z1}
+rol {z1}+1
+asl {z1}
+rol {z1}+1
+asl {z1}
+rol {z1}+1
+//FRAGMENT vwuz1=vwuz1_rol_5
+asl {z1}
+rol {z1}+1
+asl {z1}
+rol {z1}+1
+asl {z1}
+rol {z1}+1
+asl {z1}
+rol {z1}+1
+asl {z1}
+rol {z1}+1
+//FRAGMENT vwuz1=vwuz2_plus_vwuz3
+lda {z2}
+clc
+adc {z3}
+sta {z1}
+lda {z2}+1
+adc {z3}+1
+sta {z1}+1
+//FRAGMENT pbuz1=pbuz1_plus_vwuz2
+lda {z1}
+clc
+adc {z2}
+sta {z1}
+lda {z1}+1
+adc {z2}+1
+sta {z1}+1
+//FRAGMENT vwuz1=vwuz2_plus_vwuz1
+lda {z1}
+clc
+adc {z2}
+sta {z1}
+lda {z1}+1
+adc {z2}+1
+sta {z1}+1
+//FRAGMENT vbuz1=_hi_vwuz2
+lda {z2}+1
+sta {z1}
+//FRAGMENT vwuz1=vwuz2_plus_vbuz3
+lda {z3}
+clc
+adc {z2}
+sta {z1}
+lda #0
+adc {z2}+1
+sta {z1}+1
+//FRAGMENT vbuz1=_lo_vwuz2
+lda {z2}
+sta {z1}
+//FRAGMENT vbuz1=vbuz2_bor_vbuc1
+lda #{c1}
+ora {z2}
+sta {z1}
+//FRAGMENT vbuaa=_hi_vwuz1
+lda {z1}+1
+//FRAGMENT vbuxx=_hi_vwuz1
+ldx {z1}+1
+//FRAGMENT vwuz1=vwuz2_plus_vbuaa
+clc
+adc {z2}
+sta {z1}
+lda #0
+adc {z2}+1
+sta {z1}+1
+//FRAGMENT vwuz1=vwuz2_plus_vbuxx
+txa
+clc
+adc {z2}
+sta {z1}
+lda #0
+adc {z2}+1
+sta {z1}+1
+//FRAGMENT vwuz1=vwuz2_plus_vbuyy
+tya
+clc
+adc {z2}
+sta {z1}
+lda #0
+adc {z2}+1
+sta {z1}+1
+//FRAGMENT vbuaa=_lo_vwuz1
+lda {z1}
+//FRAGMENT vbuxx=_lo_vwuz1
+ldx {z1}
+//FRAGMENT vbuaa=vbuz1_bor_vbuc1
+lda #{c1}
+ora {z1}
+//FRAGMENT vbuxx=vbuz1_bor_vbuc1
+lda #{c1}
+ora {z1}
+tax
+//FRAGMENT vbuyy=vbuz1_bor_vbuc1
+lda #{c1}
+ora {z1}
+tay
+//FRAGMENT vbuz1=vbuxx_bor_vbuc1
+txa
+ora #{c1}
+sta {z1}
+//FRAGMENT vbuaa=vbuxx_bor_vbuc1
+txa
+ora #{c1}
+//FRAGMENT vbuxx=vbuxx_bor_vbuc1
+txa
+ora #{c1}
+tax
+//FRAGMENT vbuyy=vbuxx_bor_vbuc1
+txa
+ora #{c1}
+tay
+//FRAGMENT vbuz1=vbuyy_bor_vbuc1
+tya
+ora #{c1}
+sta {z1}
+//FRAGMENT vbuaa=vbuyy_bor_vbuc1
+tya
+ora #{c1}
+//FRAGMENT vbuxx=vbuyy_bor_vbuc1
+tya
+ora #{c1}
+tax
+//FRAGMENT vbuyy=vbuyy_bor_vbuc1
+tya
+ora #{c1}
+tay
+//FRAGMENT vbuyy=_lo_vwuz1
+ldy {z1}
+//FRAGMENT vbuyy=_hi_vwuz1
+ldy {z1}+1
+//FRAGMENT vwuz1=vwuz1_plus_vwuz2
+lda {z1}
+clc
+adc {z2}
+sta {z1}
+lda {z1}+1
+adc {z2}+1
+sta {z1}+1
+//FRAGMENT vwuz1=vwuz1_plus_vbuaa
+clc
+adc {z1}
+sta {z1}
+bcc !+
+inc {z1}+1
+!:
+//FRAGMENT vwuz1=vbuz2_plus_vwuz3
+lda {z2}
+clc
+adc {z3}
+sta {z1}
+lda #0
+adc {z3}+1
+sta {z1}+1
+//FRAGMENT vwuz1=vbuaa_plus_vwuz2
+clc
+adc {z2}
+sta {z1}
+lda #0
+adc {z2}+1
+sta {z1}+1
+//FRAGMENT vwuz1=vbuxx_plus_vwuz2
+txa
+clc
+adc {z2}
+sta {z1}
+lda #0
+adc {z2}+1
+sta {z1}+1
+//FRAGMENT vwuz1=vbuyy_plus_vwuz2
+tya
+clc
+adc {z2}
+sta {z1}
+lda #0
+adc {z2}+1
+sta {z1}+1
+//FRAGMENT vwuz1=vbuaa_plus_vwuz1
+clc
+adc {z1}
+sta {z1}
+bcc !+
+inc {z1}+1
+!:
+//FRAGMENT vwuz1=_deref_pbuz2_rol_1
+ldy #0
+lda ({z2}),y
+asl
+sta {z1}
+lda #0
+rol
+sta {z1}+1
+//FRAGMENT vwuz1=_deref_pbuz1_rol_1
+ldy #0
+lda ({z1}),y
+asl
+sta {z1}
+lda #0
+rol
+sta {z1}+1
+//FRAGMENT vbuz1=vbuz2_band_vbuc1
+lda #{c1}
+and {z2}
+sta {z1}
+//FRAGMENT vbuz1=_deref_pbuc1_band_pbuc2_derefidx_vbuz2
+lda {c1}
+ldy {z2}
+and {c2},y
+sta {z1}
+//FRAGMENT _deref_pbuc1=_deref_pbuc1_bor__deref_pbuc2
+lda {c1}
+ora {c2}
+sta {c1}
+//FRAGMENT vbuz1=_bnot__deref_pbuc1
+lda {c1}
+eor #$ff
+sta {z1}
+//FRAGMENT _deref_pbuc1=_deref_pbuc1_band_vbuz1
+lda {c1}
+and {z1}
+sta {c1}
+//FRAGMENT vbuaa=vbuz1_band_vbuc1
+lda #{c1}
+and {z1}
+//FRAGMENT vbuxx=vbuz1_band_vbuc1
+lda #{c1}
+and {z1}
+tax
+//FRAGMENT vbuyy=vbuz1_band_vbuc1
+lda #{c1}
+and {z1}
+tay
+//FRAGMENT vbuz1=vbuaa_band_vbuc1
+and #{c1}
+sta {z1}
+//FRAGMENT vbuaa=vbuaa_band_vbuc1
+and #{c1}
+//FRAGMENT vbuxx=vbuaa_band_vbuc1
+and #{c1}
+tax
+//FRAGMENT vbuyy=vbuaa_band_vbuc1
+and #{c1}
+tay
+//FRAGMENT vbuz1=vbuxx_band_vbuc1
+txa
+and #{c1}
+sta {z1}
+//FRAGMENT vbuaa=vbuxx_band_vbuc1
+txa
+and #{c1}
+//FRAGMENT vbuxx=vbuxx_band_vbuc1
+txa
+and #{c1}
+tax
+//FRAGMENT vbuyy=vbuxx_band_vbuc1
+txa
+and #{c1}
+tay
+//FRAGMENT vbuz1=vbuyy_band_vbuc1
+tya
+and #{c1}
+sta {z1}
+//FRAGMENT vbuaa=vbuyy_band_vbuc1
+tya
+and #{c1}
+//FRAGMENT vbuxx=vbuyy_band_vbuc1
+tya
+and #{c1}
+tax
+//FRAGMENT vbuyy=vbuyy_band_vbuc1
+tya
+and #{c1}
+tay
+//FRAGMENT vbuz1=_deref_pbuc1_band_pbuc2_derefidx_vbuaa
+tay
+lda {c1}
+and {c2},y
+sta {z1}
+//FRAGMENT vbuz1=_deref_pbuc1_band_pbuc2_derefidx_vbuxx
+lda {c1}
+and {c2},x
+sta {z1}
+//FRAGMENT vbuz1=_deref_pbuc1_band_pbuc2_derefidx_vbuyy
+lda {c1}
+and {c2},y
+sta {z1}
+//FRAGMENT vbuaa=_deref_pbuc1_band_pbuc2_derefidx_vbuz1
+lda {c1}
+ldy {z1}
+and {c2},y
+//FRAGMENT vbuaa=_deref_pbuc1_band_pbuc2_derefidx_vbuaa
+tay
+lda {c1}
+and {c2},y
+//FRAGMENT vbuaa=_deref_pbuc1_band_pbuc2_derefidx_vbuxx
+lda {c1}
+and {c2},x
+//FRAGMENT vbuaa=_deref_pbuc1_band_pbuc2_derefidx_vbuyy
+lda {c1}
+and {c2},y
+//FRAGMENT vbuxx=_deref_pbuc1_band_pbuc2_derefidx_vbuz1
+lda {c1}
+ldx {z1}
+and {c2},x
+tax
+//FRAGMENT vbuxx=_deref_pbuc1_band_pbuc2_derefidx_vbuaa
+tax
+lda {c1}
+and {c2},x
+tax
+//FRAGMENT vbuxx=_deref_pbuc1_band_pbuc2_derefidx_vbuxx
+lda {c1}
+and {c2},x
+tax
+//FRAGMENT vbuxx=_deref_pbuc1_band_pbuc2_derefidx_vbuyy
+lda {c1}
+and {c2},y
+tax
+//FRAGMENT vbuyy=_deref_pbuc1_band_pbuc2_derefidx_vbuz1
+lda {c1}
+ldy {z1}
+and {c2},y
+tay
+//FRAGMENT vbuyy=_deref_pbuc1_band_pbuc2_derefidx_vbuaa
+tay
+lda {c1}
+and {c2},y
+tay
+//FRAGMENT vbuyy=_deref_pbuc1_band_pbuc2_derefidx_vbuxx
+lda {c1}
+and {c2},x
+tay
+//FRAGMENT vbuyy=_deref_pbuc1_band_pbuc2_derefidx_vbuyy
+lda {c1}
+and {c2},y
+tay
+//FRAGMENT vbuaa=_bnot__deref_pbuc1
+lda {c1}
+eor #$ff
+//FRAGMENT vbuxx=_bnot__deref_pbuc1
+lda {c1}
+eor #$ff
+tax
+//FRAGMENT vbuyy=_bnot__deref_pbuc1
+lda {c1}
+eor #$ff
+tay
+//FRAGMENT _deref_pbuc1=_deref_pbuc1_band_vbuaa
+and {c1}
+sta {c1}
+//FRAGMENT _deref_pbuc1=_deref_pbuc1_band_vbuxx
+txa
+and {c1}
+sta {c1}
+//FRAGMENT _deref_pbuc1=_deref_pbuc1_band_vbuyy
+tya
+and {c1}
+sta {c1}

src/main/kc/include/cx16-vera.h

@@ -82,14 +82,14 @@ char * const VERA_IRQLINE_L = 0x9f28;
 // Bit 2: Chroma Disable    Setting 'Chroma Disable' disables output of chroma in NTSC composite mode and will give a better picture on a monochrome display. (Setting this bit will also disable the chroma output on the S-video output.)
 // Bit 0-1: Output Mode     0: Video disabled, 1: VGA output, 2: NTSC composite, 3: RGB interlaced, composite sync (via VGA connector)
 char * const VERA_DC_VIDEO = 0x9f29;
-char VERA_SPRITES_ENABLE = 0x40;
+const char VERA_SPRITES_ENABLE = 0x40;
-char VERA_LAYER1_ENABLE = 0x20;
+const char VERA_LAYER1_ENABLE = 0x20;
-char VERA_LAYER0_ENABLE = 0x10;
+const char VERA_LAYER0_ENABLE = 0x10;
-char VERA_CROMA_DISABLE = 0x04;
+const char VERA_CROMA_DISABLE = 0x04;
-char VERA_OUTPUT_DISABLE = 0x00;
+const char VERA_OUTPUT_DISABLE = 0x00;
-char VERA_OUTPUT_VGA = 0x01;
+const char VERA_OUTPUT_VGA = 0x01;
-char VERA_OUTPUT_NTSC = 0x02;
+const char VERA_OUTPUT_NTSC = 0x02;
-char VERA_OUTPUT_RGB = 0x03;
+const char VERA_OUTPUT_RGB = 0x03;
 // $9F2A	DC_HSCALE (DCSEL=0)	Active Display H-Scale
 char * const VERA_DC_HSCALE = 0x9f2a;
 // $9F2B	DC_VSCALE (DCSEL=0)	Active Display V-Scale
@@ -132,7 +132,7 @@ char const VERA_L0_CONFIG_HEIGHT_256 = 0xC0;
 char const VERA_L0_CONFIG_HEIGHT_MASK = 0xC0;
 unsigned int const VERA_L0_CONFIG_HEIGHT[4] = { 32, 64, 128, 256 };
 // $9F2E	L0_MAPBASE	    Layer 0 Map Base Address (16:9)
-char * const VERA_L0_MAPBASE = 0x9f2e;
+unsigned byte * const VERA_L0_MAPBASE = 0x9f2e;
 // $9F2F	L0_TILEBASE	    Layer 0 Tile Base
 // Bit 2-7: Tile Base Address (16:11)
 // Bit 1:   Tile Height (0:8 pixels, 1:16 pixels)

src/main/kc/lib/conio-cx16.c

@@ -6,10 +6,22 @@
 #define CONIO_WIDTH conio_screen_width
 // The screen height
 #define CONIO_HEIGHT conio_screen_height
-// The text screen address
+// The text screen base address, which is a 16:0 bit value in VERA VRAM.
-char * const CONIO_SCREEN_TEXT = DEFAULT_SCREEN;
+// That is 128KB addressable space, thus 17 bits in total.
+// CONIO_SCREEN_TEXT contains bits 15:0 of the address.
+// CONIO_SCREEN_BANK contains bit 16, the the 64K memory bank in VERA VRAM (the upper 17th bit).
+// !!! note that these values are not const for the cx16!
+// This conio implements the two layers of VERA, which can be layer 0 or layer 1.
+// Configuring conio to output to a different layer, will change these fields to the address base
+// configured using VERA_L0_MAPBASE = 0x9f2e or VERA_L1_MAPBASE = 0x9f35.
+// Using the function setscreenlayer(layer) will re-calculate using CONIO_SCREEN_TEXT and CONIO_SCREEN_BASE
+// based on the values of VERA_L0_MAPBASE or VERA_L1_MAPBASE, mapping the base address of the selected layer.
+// The function setscreenlayermapbase(layer,mapbase) allows to configure bit 16:9 of the
+// mapbase address of the time map in VRAM of the selected layer VERA_L0_MAPBASE or VERA_L1_MAPBASE.
+char* CONIO_SCREEN_TEXT = DEFAULT_SCREEN;
+byte CONIO_SCREEN_BANK = 0; // Default screen of the CX16 emulator uses memory bank 0 for text.
 // The color screen address
-char * const CONIO_SCREEN_COLORS = COLORRAM;
+char* const CONIO_SCREEN_COLORS = COLORRAM;
 // The default text color
 const char CONIO_TEXTCOLOR_DEFAULT = WHITE;
 // The default back color
@@ -23,13 +35,16 @@ void conio_x16_init() {
     // Position cursor at current line
     char * const BASIC_CURSOR_LINE = 0xD6;
     char line = *BASIC_CURSOR_LINE;
-    screensize( &conio_screen_width, &conio_screen_height );
+    screensize(&conio_screen_width, &conio_screen_height);
+    screenlayer(1);
+    setscreenlayermapbase(0,0x00);
+    setscreenlayermapbase(1,0x00);
     if(line>=CONIO_HEIGHT) line=CONIO_HEIGHT-1;
     gotoxy(0, line);
 }
 
 // Return true if there's a key waiting, return false if not
-unsigned char kbhit (void) {
+unsigned char kbhit(void) {
     // CIA#1 Port A: keyboard matrix columns and joystick #2
     char* const CIA1_PORT_A = 0xdc00;
     // CIA#1 Port B: keyboard matrix rows and joystick #1.
@@ -88,11 +103,14 @@ __ma unsigned byte conio_scroll_enable = 1;
 __ma unsigned byte conio_screen_width = 0;
 // Variable holding the screen height;
 __ma unsigned byte conio_screen_height = 0;
+// Variable holding the screen layer on the VERA card with which conio interacts;
+__ma unsigned byte conio_screen_layer = 1;
+//
+__ma unsigned byte* conio_screen_layer_mapbase[2] = {VERA_L0_MAPBASE, VERA_L1_MAPBASE};
 
 // clears the screen and moves the cursor to the upper left-hand corner of the screen.
 void clrscr(void) {
     char* line_text = CONIO_SCREEN_TEXT;
-    char* line_cols = CONIO_SCREEN_COLORS;
     unsigned int conio_width = VERA_L1_CONFIG_WIDTH[ ( (*VERA_L1_CONFIG) & VERA_L1_CONFIG_WIDTH_MASK ) >> 4 ];
     unsigned int conio_height = VERA_L1_CONFIG_HEIGHT[ ( (*VERA_L1_CONFIG) & VERA_L1_CONFIG_HEIGHT_MASK ) >> 6 ];
     char color = ( conio_backcolor << 4 ) | conio_textcolor;
@@ -103,7 +121,7 @@ void clrscr(void) {
         // Set address
         *VERA_ADDRX_L = <ch;
         *VERA_ADDRX_M = >ch;
-        *VERA_ADDRX_H = VERA_INC_1;
+        *VERA_ADDRX_H = CONIO_SCREEN_BANK | VERA_INC_1;
         for( char c=0;c<conio_width; c++ ) {
             // Set data
             *VERA_DATA0 = ' ';
@@ -114,12 +132,10 @@ void clrscr(void) {
             //line_cols[c] = conio_textcolor;
         }
         line_text += 256;
-        line_cols += 256;
     }
     conio_cursor_x = 0;
     conio_cursor_y = 0;
     conio_line_text = CONIO_SCREEN_TEXT;
-    conio_line_color = CONIO_SCREEN_COLORS;
 }
 
 // Set the cursor to the specified position
@@ -130,15 +146,77 @@ void gotoxy(unsigned byte x, unsigned byte y) {
     conio_cursor_y = y;
     unsigned int line_offset = (unsigned int)y << 8;
     conio_line_text = CONIO_SCREEN_TEXT + line_offset;
-    conio_line_color = CONIO_SCREEN_COLORS + line_offset;
 }
 
+// Set the layer with which the conio will interact.
+// - layer: value of 0 or 1.
+void screenlayer(unsigned byte layer) {
+    if(layer > 1)
+        layer = 1;
+    conio_screen_layer = layer;
+    unsigned byte* addr = conio_screen_layer_mapbase[layer];
+    unsigned int addr_i = *addr << 1;
+    CONIO_SCREEN_BANK = >addr_i;
+    CONIO_SCREEN_TEXT = addr_i << 8;
+}
+
+// Set the base of the map layer with which the conio will interact.
+// - layer: Value of 0 or 1.
+// - mapbase: Specifies the base address of the tile map.
+//   Note that the register only specifies bits 16:9 of the address,
+//   so the resulting address in the VERA VRAM is always aligned to a multiple of 512 bytes.
+void setscreenlayermapbase(unsigned byte layer, unsigned byte mapbase) {
+    if(layer > 1)
+        layer = 1;
+    unsigned byte* addr = conio_screen_layer_mapbase[layer];
+    *addr = mapbase;
+}
+
+// Get the base of the map layer with which the conio will interact.
+// - layer: Value of 0 or 1.
+// - return: Returns the base address of the tile map.
+//   Note that the register is a byte, specifying only bits 16:9 of the address,
+//   so the resulting address in the VERA VRAM is always aligned to a multiple of 512 bytes.
+unsigned byte getscreenlayermapbase(unsigned byte layer) {
+    if(layer > 1)
+        layer = 1;
+    unsigned byte* mapbase = conio_screen_layer_mapbase[layer];
+    return *mapbase;
+}
+
+
+// Enable the layer to be displayed on the screen.
+// - layer: 0 or 1.
+void screenlayerenable(unsigned byte layer) {
+    unsigned char enable[2] = { VERA_LAYER0_ENABLE, VERA_LAYER1_ENABLE };
+    layer &= $1;
+    *VERA_DC_VIDEO |= enable[layer];
+}
+
+// Disable the layer to be displayed on the screen.
+// - layer: 0 or 1.
+void screenlayerdisable(unsigned byte layer) {
+    const unsigned byte disable[2] = { VERA_LAYER0_ENABLE, VERA_LAYER1_ENABLE };
+    layer &= $1;
+    *VERA_DC_VIDEO &= ~disable[layer];
+}
+
+
+// Is the layer displayed on the screen?
+// - returns: 1 if layer is displayed on the screen, 0 if not.
+unsigned byte screenlayerenabled(unsigned byte layer) {
+    const unsigned byte enabled[2] = { VERA_LAYER0_ENABLE, VERA_LAYER1_ENABLE };
+    layer &= $1;
+    return *VERA_DC_VIDEO & enabled[layer];
+}
+
+
 // Return the current screen size.
 void screensize(unsigned byte* x, unsigned byte* y) {
     // VERA returns in VERA_DC_HSCALE the value of 128 when 80 columns is used in text mode,
     // and the value of 64 when 40 columns is used in text mode.
     // Basically, 40 columns mode in the VERA is a double scan mode.
-    // Same for the VERA_DC_VSCALE mode.
+    // Same for the VERA_DC_VSCALE mode, but then the subdivision is 60 or 30 rows.
     // I still need to test the other modes, but this will suffice for now for the pure text modes.
     char hscale = (*VERA_DC_HSCALE) >> 7;
     *x = 40 << hscale;
@@ -171,16 +249,18 @@ inline unsigned byte wherey(void) {
 // Moves the cursor forward. Scrolls the entire screen if needed
 void cputc(char c) {
     char color = ( conio_backcolor << 4 ) | conio_textcolor;
+    unsigned byte* conio_addr = CONIO_SCREEN_TEXT;
+    conio_addr += conio_cursor_y*256;
+    conio_addr += conio_cursor_x << 1;
     if(c=='\n') {
         cputln();
     } else {
         // Select DATA0
         *VERA_CTRL &= ~VERA_ADDRSEL;
         // Set address
-        char lx = conio_cursor_x << 1;
+        *VERA_ADDRX_L = <conio_addr;
-        *VERA_ADDRX_L = <(conio_line_text+lx);
+        *VERA_ADDRX_M = >conio_addr;
-        *VERA_ADDRX_M = >(conio_line_text+lx);
+        *VERA_ADDRX_H = CONIO_SCREEN_BANK | VERA_INC_1;
-        *VERA_ADDRX_H = VERA_INC_1;
         *VERA_DATA0 = c;
         *VERA_DATA0 = color;
 

src/test/kc/examples/cx16/veralayers.c

@@ -0,0 +1,53 @@
+#include <printf.h>
+
+void main() {
+    textcolor(BLUE);
+    backcolor(BLACK);
+    clrscr();
+    // This statement sets the base of the display layer 1 at VRAM address 0x0200
+    setscreenlayermapbase(0,0x20);
+    screenlayer(0);
+    clrscr();
+    screenlayer(1);
+
+    gotoxy(0,0);
+
+    gotoxy(0,16);
+    textcolor(RED);
+    unsigned int width = screensizex();
+    unsigned int height = screensizey();
+    printf("vera card width = %u; height = %u\n", width, height);
+
+    printf("dc video = %x\n", *VERA_DC_VIDEO);
+    printf("vera card layer 0 enabled = %x\n", screenlayerenabled(0));
+    printf("vera card mapbase layer 0 = %x\n", getscreenlayermapbase(0));
+    printf("l0 config = %x\n", *VERA_L0_CONFIG);
+    printf("l0 tilebase = %x\n", *VERA_L0_TILEBASE);
+    printf("l0 vscroll l = %x\n", *VERA_L0_HSCROLL_L);
+    printf("l0 vscroll h = %x\n", *VERA_L0_HSCROLL_H);
+    printf("vera card layer 1 enabled = %x\n", screenlayerenabled(1));
+    printf("vera card mapbase layer 1 = %x\n", getscreenlayermapbase(1));
+    printf("l1 config = %x\n", *VERA_L1_CONFIG);
+    printf("l1 tilebase = %x\n", *VERA_L1_TILEBASE);
+    printf("l1 vscroll l = %x\n", *VERA_L1_HSCROLL_L);
+    printf("l1 vscroll h = %x\n", *VERA_L1_HSCROLL_H);
+
+    textcolor(BLUE);
+    //disablescreenlayer1();
+    screenlayerenable(0);
+    printf("dc video = %x\n", *VERA_DC_VIDEO);
+    printf("vera card layer 0 enabled = %x\n", screenlayerenabled(0));
+    printf("vera card layer 1 enabled = %x\n", screenlayerenabled(1));
+    printf("vera card mapbase layer 0 = %x\n", getscreenlayermapbase(0));
+    printf("vera card mapbase layer 1 = %x\n", getscreenlayermapbase(1));
+    printf("vera card mapbase layer 1 = %x\n", getscreenlayermapbase(1));
+
+    screenlayer(0);
+    gotoxy(0,0);
+    textcolor(GREEN);
+    *VERA_L0_CONFIG = *VERA_L1_CONFIG;
+    *VERA_L0_TILEBASE = *VERA_L1_TILEBASE;
+    printf("this is printed on layer 0");
+
+    //screenlayerdisable(0);
+}