emulate crosstalk display artifact

rtl/apple1.v

@@ -43,13 +43,12 @@ module apple1(
 	 // interrupt signa
 	 input INT_n,
 
-    // Outputs to VGA display
-    output vga_h_sync,          // hozizontal VGA sync pulse
-    output vga_v_sync,          // vertical VGA sync pulse
-    output vga_red,             // red VGA signal
-    output vga_grn,             // green VGA signal
-    output vga_blu,             // blue VGA signal
-    input vga_cls,              // clear screen button
+    // video outputs
+    output       vga_h_sync,          // hozizontal sync pulse
+    output       vga_v_sync,          // vertical sync pulse
+    output [5:0] vga_red,             // red signal
+    output [5:0] vga_grn,             // green signal
+    output [5:0] vga_blu,             // blue signal    
 	 
 	 output reset_key,           // keyboard shortcut for reset
 	 output poweroff_key         // keyboard shortcut for poweroff/on

rtl/apple1_mist.sv

@@ -15,10 +15,10 @@
 // TODO keyboard: isolate ps2 keyboard from apple1
 // TODO keyboard: check ps2 clock
 // TODO keyboard: make a true ascii keyboard
+// TODO keyboard: why can't be reset hit twice ?
 // TODO osd menu yellow, why it doesn't work?
 // TODO display: check NTSC AD724 hsync problem
-// TODO display: powerup values
-// TODO display: simplify rom font
+// TODO display: blinking at powerup
 // TODO display: reduce to 512 bytes font
 // TODO display: check parameters vs real apple1
 // TODO display: check cursor blinking vs 555 timings
@@ -88,10 +88,6 @@ localparam conf_str_len = $size(CONF_STR)>>3;
 
 wire st_reset_switch = buttons[1];
 
-
-wire r, g, b;
-wire hs, vs;
-
 wire [31:0] status;
 wire  [1:0] buttons;
 wire  [1:0] switches;
@@ -306,6 +302,11 @@ wire [7:0] bus_dout = rom_cs   ? rom_dout   :
 wire reset_key;
 wire poweroff_key;							 
 
+wire [5:0] r;
+wire [5:0] g;
+wire [5:0] b;
+wire hs, vs;
+
 // detects the rising edge of the keyboard reset key
 // otherwise keyboard stays in reset mode
 wire reset_key_edge = reset_key_old == 0 && reset_key == 1; 
@@ -357,7 +358,7 @@ apple1 apple1
 
 mist_video 
 #(
-	.COLOR_DEPTH(1),    // 1 bit color depth
+	.COLOR_DEPTH(6),    // 1 bit color depth
 	.OSD_AUTO_CE(1),    // OSD autodetects clock enable
 	.OSD_COLOR(3'b110), // yellow menu color
 	.SYNC_AND(1),

rtl/display.v

@@ -8,11 +8,11 @@ module display (
 	 input clr_screen,       // clear screen button
 	 
 	 // video output	
-    output vga_h_sync,      // horizontal VGA sync pulse
-    output vga_v_sync,      // vertical VGA sync pulse
-    output vga_red,         // red VGA signal
-    output vga_grn,         // green VGA signal
-    output vga_blu,         // blue VGA signal
+    output       vga_h_sync, // horizontal sync pulse
+    output       vga_v_sync, // vertical sync pulse
+    output [5:0] vga_red,    // red signal
+    output [5:0] vga_grn,    // green signal
+    output [5:0] vga_blu,    // blue signal
 	 
 	 output reg ready,       // display ready (PB7 of CIA)
 
@@ -184,11 +184,15 @@ module display (
     assign font_pixel = h_dot;     
                                    
     assign font_line = v_dot * 2 + 4;
+	 
+	 wire cross_talk_artifact = (h_active & v_active) && v_dot == 0 && h_dot == 0;
+	 
+	 wire [5:0] pixel_out = { font_out, font_out, font_out, font_out, font_out | cross_talk_artifact, font_out };
 
     // vga signals out to monitor
-    assign vga_red = (h_active & v_active) ? font_out : 1'b0;
-    assign vga_grn = (h_active & v_active) ? font_out : 1'b0;    
-	 assign vga_blu = (h_active & v_active) ? font_out : 1'b0;
+    assign vga_red = (h_active & v_active) ? pixel_out : 6'b0;
+    assign vga_grn = (h_active & v_active) ? pixel_out : 6'b0;    
+	 assign vga_blu = (h_active & v_active) ? pixel_out : 6'b0;
 
     assign vga_h_sync = (h_cnt < h_pulse) ? 0 : 1;
     assign vga_v_sync = (v_cnt < v_pulse) ? 0 : 1;

rtl/font_rom.v

@@ -30,12 +30,14 @@ module font_rom (
     );
 
     reg [7:0] rom[0:1023];
+	 //reg [7:0] rom[0:511];
 
     initial
         $readmemh("roms/vga_font_bitreversed.hex", rom, 0, 1023);
+		  //$readmemb("roms/s2513.bin", rom, 0, 511);
 
     // double height of pixel by ignoring bit 0
-    wire [3:0] line_ptr = line[4:1];
+    wire [3:0] line_ptr = line[4:1];	 
 
     // Note: Quartus II reverses the pixels when we do:
     //
@@ -53,6 +55,7 @@ module font_rom (
     always @(posedge clk)
     begin
         romout = rom[(character * 10) + {2'd0, line_ptr}];
+		  //romout = rom[(character * 8) + {2'd0, line_ptr}];
         
         out <= romout[pixel];
     end