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// 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