Support double height textCVS: ----------------------------------------------------------------------

1 files changed, 29 insertions, 9 deletions

diff --git a/display.v b/display.v
index 6dca8a7..381a13c 100644
--- a/display.v
+++ b/display.v
@@ -80,6 +80,7 @@ module display (
    reg [9:0] 	 x;		// Horizontal pixel count
    reg [8:0] 	 y;		// Vertical pixel count
    wire [10:0] 	 a80;		// Character row assuming 80 columns
+   wire [10:0] 	 a80u;		// Character row assuming 80 columns (up 1 line)
    reg [5:0] 	 scan_counter;	// Counter of total scans (for flashing et al)
    reg [7:0] 	 pixrow;	// One character worth of pixels
    reg [2:0] 	 fg;		// Foreground RGB
@@ -89,28 +90,37 @@ module display (
    reg 		 isgsep;	// Separated graphics?
    reg 		 isgrel;	// Hold graphics?
    reg 		 isdble;	// Double height?
+   reg 		 wasdble;	// Double height (previous row)
    reg 		 isflsh;	// Flashing?
    reg 		 ishide;	// Hidden
    reg [7:0] 	 thischar;	// Character code currently processing
-   wire [3:0] 	 xmiddle;	// Used in address calculation
-   wire [3:0] 	 ymiddle;	// Used in address calculation
    wire 	 xvideo;	// Non-blanked in the x direction
    wire 	 yvideo;	// Non-blanked in the y direction
    
    // Address mapping for 80 characters; for 40 characters
    // we shift this left by 1
    assign 	 a80[3:0] = x[6:3];
-   assign 	 xmiddle = { 1'b0, x[9:7] };
-   assign 	 ymiddle = { y[8:7], y[8:7] };
+   wire [3:0] 	 xmiddle = { 1'b0, x[9:7] };
+   wire [3:0] 	 ymiddle = { y[8:7] , y[8:7] };
    assign 	 a80[7:4] = xmiddle+ymiddle;
    assign 	 a80[10:8] = y[6:4];
 
+   // Address mapping for 80 characters minus one line
+   wire [4:0] 	 ylu = y[8:4] - 1;
+   assign 	 a80u[3:0] = x[6:3];
+   wire [3:0] 	 yumiddle = { ylu[4:3] , ylu[4:3] };
+   assign 	 a80u[7:4] = xmiddle+yumiddle;
+   assign 	 a80u[10:8] = ylu[2:0];
+
    // Final address mapping
-   assign 	 a = width ? a80[10:0] : { 1'b1, a80[10:1] };
+   // Note: We read the current char between pixels 0 and 1,
+   // and the char above between pixels 2 and 3; hence the use of x[1].
+   wire [10:0] 	 amap = x[1] ? a80u : a80;
+   assign 	 a = width ? amap[10:0] : { 1'b1, amap[10:1] };
 
    // Character generator address mapping
    assign 	 ga[10:4] = thischar[6:0];
-   assign 	 ga[3:0] = y[3:0];
+   assign 	 ga[3:0]  = wasdble ? { 1'b1, y[3:1] } : isdble ? { 0'b0, y[3:1] } : y[3:0];
 
    // Video enable signal
    assign 	 xvideo = ( x < x_blank );
@@ -160,11 +170,20 @@ module display (
 	if ( width | ~x[3] )
 	  begin
 	     case ( x[2:0] )
-	       3'b011:
+	       3'b001:
 		 begin
 		    // Load and process character
 		    thischar <= d;
 		 end
+
+	       3'b011:
+		 begin
+		    if ( (y[8:4] != 0) && (d[6:1] == 6'b000110) )
+		      wasdble <= d[0];
+
+		    if ( wasdble )
+		      thischar <= d;
+		 end
 	       
 	       3'b111:
 		 begin
@@ -192,12 +211,12 @@ module display (
 				  isgsep <= 1'b0;
 				5'b11010:
 				  isgsep <= 1'b1;
-				5'b11100:
+				5'b11100: // BLBG
 				  begin
 				     bg <= 3'b000;
 				     fg <= bg;
 				  end
-				5'b11101:
+				5'b11101: // NWBG
 				  begin
 				     bg <= fg;
 				     fg <= 3'b000;
@@ -296,6 +315,7 @@ module display (
 	     isflsh <= 0;	// Not flashing
 	     isgsep <= 0;	// Not separated
 	     isdble <= 0;	// Not double
+	     wasdble <= 0;	// Not double
 	     isgrel <= 1;	// Release graphics
 	     ishide <= 0;	// Not hidden
 	     pixrow <= 8'b0;	// Read-ahead spot is blank