Author: Rejean Lau 
Date: Nov 17, 2004


This is a SVGA controller for the Virtex II multimedia board.
It outputs a purple screen as output, using a 50 MHz pixel clock.

It is based on the design example on the Virtex II multimedia web site
for BitMapped SVGA controller on http://www.xilinx.com/products/boards/multimedia/
examples.htm



There is a mistake in the design example as they were not inverting
their blanking signal, as stated in the user guide.
(blanking signal active low). I suspected this when
I was getting purple, at the corner of my screen
(everywhere it should not be blanked).

So, I made the following adjustments



         // CREATE THE COMPOSITE BANKING SIGNAL
         always @ (posedge pixel_clock or posedge reset) begin
         if (reset)
         begin // on reset
         //blank <= 1'b0; 
         blank <= 1'b1;  //remove blank
         end

         else if (h_blank || v_blank) // blank during HBI or VBI
         begin
         //blank <= 1'b1;
         blank <= 1'b0;
         end
         else begin
         //blank <= 1'b0; 
         blank <= 1'b1; // active video do not blank
         end
         end