Top secrets sources NedoPC pentevo

// ZX-Evo Base Configuration (c) NedoPC 2008,2009,2010,2011,2012,2013,2014
//
// renders fetched video data to the pixels

/*
    This file is part of ZX-Evo Base Configuration firmware.

    ZX-Evo Base Configuration firmware is free software:
    you can redistribute it and/or modify it under the terms of
    the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    ZX-Evo Base Configuration firmware is distributed in the hope that
    it will be useful, but WITHOUT ANY WARRANTY; without even
    the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
    See the GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with ZX-Evo Base Configuration firmware.
    If not, see <http://www.gnu.org/licenses/>.
*/

`include "../include/tune.v"

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

        // ulaplus related
        output wire [ 1:0] up_palsel,
        output wire [ 2:0] up_paper,
        output wire [ 2:0] up_ink,
        output wire        up_pixel,


        input  wire [10:0] fnt_a,
        input  wire [ 7:0] fnt_d,
        input  wire        fnt_wr,




        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,    //


        output wire [ 7:0] fontrom_readback
);


        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;



        // ulaplus signals
        assign up_pixel  = pixbit;
        //
        assign up_palsel = attrbyte[7:6];
        //
        assign up_paper  = attrbyte[5:3];
        assign up_ink    = attrbyte[2:0];




        wire rom_ena;
        assign rom_ena = ena_pix & ginc;

        video_fontrom video_fontrom(

                .clock (clk ),
                /*.enable(1'b1),*/

                .data     (fnt_d ),
                .wraddress(fnt_a ),
                .wren     (fnt_wr),

                .rdaddress( {pixbyte, typos} ),
                .rden     ( rom_ena          ),
                .q        ( symbyte          )
        );


        assign fontrom_readback = symbyte;


endmodule