`include "../include/tune.v"
// Pentevo project (c) NedoPC 2011
//
// renders fetched video data to the pixels
module video_render(
input wire clk, // 28 MHz clock
input wire [63:0] pic_bits, // video data from fetcher
input wire fetch_sync, // synchronizes pixel rendering -
// coincides with cbeg!!!
input wire cbeg,
input wire post_cbeg, // pixel strobed and
input wire pre_cend,
input wire cend, // general sync
input wire int_start, // for flash gen
input wire [ 2:0] typos, // Y pos in text symbols
output wire [ 3:0] pixels, // output pixels
input wire mode_atm_n_pent, // decoded modes
input wire mode_zx, //
input wire mode_p_16c, //
input wire mode_p_hmclr, //
//
input wire mode_a_hmclr, //
input wire mode_a_16c, //
input wire mode_a_text, //
input wire mode_pixf_14 //
);
reg [4:0] flash_ctr;
wire flash;
initial
begin
flash_ctr = 0;
end
always @(posedge clk) if( int_start )
begin
flash_ctr <= flash_ctr + 1;
end
assign flash = flash_ctr[4];
// fetched data divided in bytes
wire [7:0] bits [0:7];
assign bits[0] = pic_bits[ 7:0 ];
assign bits[1] = pic_bits[15:8 ];
assign bits[2] = pic_bits[23:16];
assign bits[3] = pic_bits[31:24];
assign bits[4] = pic_bits[39:32];
assign bits[5] = pic_bits[47:40];
assign bits[6] = pic_bits[55:48];
assign bits[7] = pic_bits[63:56];
reg [1:0] gnum; // pixel group number
reg [2:0] pnum; // pixel number
wire [1:0] gadd;
wire [2:0] padd;
wire ginc;
wire modes_16c;
wire modes_zxattr;
wire ena_pix;
assign ena_pix = cend | (mode_pixf_14 & post_cbeg);
assign modes_16c = mode_p_16c | mode_a_16c;
assign modes_zxattr = mode_zx | mode_p_hmclr;
assign {ginc, padd} = {1'b0, pnum} + {2'b00, modes_16c, ~modes_16c};
always @(posedge clk) if( ena_pix )
if( fetch_sync )
pnum <= 3'b000;
else
pnum <= padd;
assign gadd = gnum + ( {modes_zxattr,~modes_zxattr} & {2{ginc}} );
always @(posedge clk) if( ena_pix )
if( fetch_sync )
gnum <= 2'b00;
else
gnum <= gadd;
wire [15:0] pgroup; // pixel group
wire [7:0] pixbyte, symbyte, attrbyte;
wire [7:0] pix16_2 [0:1];
wire [3:0] pix16 [0:3];
wire pixbit; // pixel bit, for attr modes
wire [3:0] pix0, pix1; // colors for bit=0 and bit=1, for attr modes
wire [3:0] apix, c16pix;
assign pgroup = { bits[ {gnum[0], 1'b0, gnum[1]} ] ,
bits[ {gnum[0], 1'b1, gnum[1]} ] };
assign pixbyte = pgroup[15:8];
assign attrbyte = pgroup[ 7:0];
assign pix16_2[0] = pgroup[ 7:0];
assign pix16_2[1] = pgroup[15:8];
assign pix16[0] = { pix16_2[0][6], pix16_2[0][2:0] };
assign pix16[1] = { pix16_2[0][7], pix16_2[0][5:3] };
assign pix16[2] = { pix16_2[1][6], pix16_2[1][2:0] };
assign pix16[3] = { pix16_2[1][7], pix16_2[1][5:3] };
assign pixbit = mode_a_text ? symbyte[~pnum] : pixbyte[~pnum];
assign pix0 = { (modes_zxattr ? attrbyte[6] : attrbyte[7]), attrbyte[5:3] }; // paper
assign pix1 = { attrbyte[6], attrbyte[2:0] }; // ink
assign apix = ( pixbit^(modes_zxattr & flash & attrbyte[7]) ) ? pix1 : pix0;
assign c16pix = pix16[ pnum[2:1] ];
assign pixels = modes_16c ? c16pix : apix;
wire rom_ena;
assign rom_ena = ena_pix & ginc;
video_fontrom video_fontrom(
.clock(clk),
.enable(rom_ena),
.data(8'd0),
.wraddress(11'd0),
.wren(1'b0),
.rdaddress( {pixbyte, typos} ),
.rden(1'b1),
.q( symbyte )
);
endmodule