Fix bugs in the new display.v

Fix bugs in the new 6x10 display.v, mostly involving using the wrong
counter bits in various places.

1 files changed, 39 insertions, 15 deletions

diff --git a/display.v b/display.v
index 3ac13e9..55aa914 100644
--- a/display.v
+++ b/display.v
@@ -7,7 +7,7 @@ module display (
 		input            testpattern,
 		input            reveal,
 		
-		output    [10:0] a,
+		output reg [10:0] a,
 		input      [7:0] d,
 		output    [10:0] ga,
 		input      [5:0] gd,
@@ -78,6 +78,8 @@ module display (
    wire 	 yvideo;	// Non-blanked in the y direction
    wire [10:0] 	 a80;		// Memory address assuming 80 columns
    wire [10:0] 	 a80u;		// Memory address assuming 80 columns (-1 line)
+   wire [10:0] 	 a40;		// Memory address assuming 40 columns
+   wire [10:0] 	 a40u;		// Memory address assuming 40 columns (-1 line)
    reg [4:0] 	 scan_counter;	// Counter of total scans (for flashing et al)
    reg [5:0] 	 pixrow;	// One character worth of pixels
    reg 		 prefetch;	// True for the prefetch character position
@@ -116,25 +118,42 @@ module display (
    // Should we advance the character pixel?
    wire 	 advance = width | x[0];
    
-   // Address mapping for 80 characters; for 40 characters
-   // we shift this left by 1
+   // Address mapping for 40 and 80 characters
    assign 	 a80[3:0] = xchr[3:0];
-   wire [3:0] 	 xmiddle = { 1'b0, xchr[6:4] };
+   wire [3:0] 	 x80middle = { 1'b0, xchr[6:4] };
    wire [3:0] 	 ymiddle = { ychr[4:3] , ychr[4:3] };
-   assign 	 a80[7:4] = xmiddle+ymiddle;
+   assign 	 a80[7:4] = x80middle+ymiddle;
    assign 	 a80[10:8] = ychr[2:0];
 
-   // Address mapping for 80 characters minus one line
+   assign        a40[2:0] = xchr[2:0];
+   wire [3:0] 	 x40middle = { 1'b0, xchr[5:3] };
+   assign 	 a40[6:3] = x40middle + ymiddle;
+   assign 	 a40[10:7] = { 1'b1, ychr[2:0] };
+
+   // Address mapping for 40 and 80 characters minus one line
    assign 	 a80u[3:0] = xchr[3:0];
    wire [3:0] 	 yumiddle = { ylu[4:3] , ylu[4:3] };
-   assign 	 a80u[7:4] = xmiddle+yumiddle;
+   assign 	 a80u[7:4] = x80middle+yumiddle;
    assign 	 a80u[10:8] = ylu[2:0];
 
+   assign 	 a40u[2:0] = xchr[2:0];
+   assign 	 a40u[6:3] = x40middle+yumiddle;
+   assign 	 a40u[10:7] = { 1'b1, ylu[2:0] };
+
    // Final address mapping
    // Note: We read the current char between pixels 0 and 1,
-   // and the char above between pixels 2 and 3; hence the use of xchr[1].
-   wire [10:0] 	 amap = xchr[1] ? a80u : a80;
-   assign 	 a = width ? amap[10:0] : { 1'b1, amap[10:1] };
+   // and the char above between pixels 2 and 3; hence the use of xpxl[1].
+   always @(*)
+     case ( { width, xpxl[1] } )
+       2'b00:
+	 a = a40;
+       2'b01:
+	 a = a40u;
+       2'b10:
+	 a = a80;
+       2'b11:
+	 a = a80u;
+     endcase // case( { width, xchr[1] } )
 
    // Character generator address mapping
    assign 	 ga[10:4] = somechar[6:0];
@@ -274,7 +293,9 @@ module display (
 
 			 // Character generation
 
-			 if ( wasdble ? (wasgraph & thatchar[5]) : (isgraph & thischar[5]) )
+			 if ( wasdble
+			      ? (wasgraph & thatchar[5])
+			      : (isgraph & thischar[5]) )
 			   begin
 			      // Generate graphical character
 			      case ( ga[3:0] )
@@ -336,13 +357,16 @@ module display (
 				  pixrow <= 5'bxxxxxx;
 			      endcase // case( ga[3:0] )
 			   end // if ( wasdble ? (wasgraph & thatchar[5]) : (isgraph & thischar[5]) )
-			 else if ( (somechar[6:5] != 2'b00) | (wasdble ? wasgrel : isgrel) )
+			 else if ( (somechar[6:5] != 2'b00) |
+				   (wasdble ? wasgrel : isgrel) )
 			   pixrow <= gd; // Input from character ROM
 
+			 // Flash/inverse
+			 inverse <= somechar[7];
+
 			 // This is no longer a prefetch character...
 			 prefetch <= 1'b0;
 		      end // if ( xvideo )
-		    inverse <= somechar[7];
 		 end // case: 3'b101
 	     endcase // case( xpxl )
 	  end // if ( advance )
@@ -353,7 +377,7 @@ module display (
 	     x <= 10'd0;
 	     xchr <= 7'd0;
 	     xpxl <= 3'd0;
-	     pixrow <= 8'b0;	// Read-ahead spot is blank
+	     pixrow <= 6'b0;	// Read-ahead spot is blank
 	     prefetch <= 1'b1;	// Prefetch character
 	     inverse <= 1'b0;	// Not inverse video
 	     curfg <= 3'b111;	// Default fg is white
@@ -397,7 +421,7 @@ module display (
 	  end // if ( x == x_max-1 )
 	else
 	  begin
-	     if ( width | x[0] )
+	     if ( advance )
 	       begin
 		  if ( xpxl == 3'd5 )
 		    begin