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//

// chrgen.v -- character generator

//

module chrgen(clk, pixclk,

              chrcode, chrrow, chrcol,

              pixel,

              attcode_in, blank_in, hsync_in, vsync_in, blink_in,

              attcode_out, blank_out, hsync_out, vsync_out, blink_out);

    input clk;

    input pixclk;

    input [7:0] chrcode;

    input [3:0] chrrow;

    input [2:0] chrcol;

    output pixel;

    input [7:0] attcode_in;

    input blank_in;

    input hsync_in;

    input vsync_in;

    input blink_in;

    output reg [7:0] attcode_out;

    output reg blank_out;

    output reg hsync_out;

    output reg vsync_out;

    output reg blink_out;

  wire [13:0] addr;

  wire [0:0] pixel_lo;

  wire [0:0] pixel_hi;

  reg mux_ctrl;

  assign addr[13:7] = chrcode[6:0];

  assign addr[6:3] = chrrow[3:0];

  assign addr[2:0] = chrcol[2:0];

  assign pixel = (mux_ctrl == 0) ? pixel_lo[0] : pixel_hi[0];

  // RAMB16_S1: Spartan-3 16kx1 Single-Port RAM

  RAMB16_S1 character_rom_lo (

    .DO(pixel_lo),  // 1-bit Data Output

    .ADDR(addr),    // 14-bit Address Input

    .CLK(clk),      // Clock

    .DI(1'b0),      // 1-bit Data Input

    .EN(pixclk),    // RAM Enable Input

    .SSR(1'b0),     // Synchronous Set/Reset Input

    .WE(1'b0)       // Write Enable Input

  );

  `include "chrgenlo.init"

  // RAMB16_S1: Spartan-3 16kx1 Single-Port RAM

  RAMB16_S1 character_rom_hi (

    .DO(pixel_hi),  // 1-bit Data Output

    .ADDR(addr),    // 14-bit Address Input

    .CLK(clk),      // Clock

    .DI(1'b0),      // 1-bit Data Input

    .EN(pixclk),    // RAM Enable Input

    .SSR(1'b0),     // Synchronous Set/Reset Input

    .WE(1'b0)       // Write Enable Input

  );

  `include "chrgenhi.init"

  always @(posedge clk) begin

    if (pixclk == 1) begin

      attcode_out[7:0] <= attcode_in[7:0];

      blank_out <= blank_in;

      hsync_out <= hsync_in;

      vsync_out <= vsync_in;

      blink_out <= blink_in;

      mux_ctrl <= chrcode[7];

    end

  end

endmodule