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//============================================================================

// Test Sinclair ZX Spectrum ULA

//

//  Copyright (C) 2014-2016  Goran Devic

//

//  This program 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 2 of the License, or (at your option)

//  any later version.

//

//  This program 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 this program; if not, write to the Free Software Foundation, Inc.,

//  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

//============================================================================

module test_ula

(

    input wire CLOCK_50,        // Input clock 50 MHz

    input wire CLOCK_27,        // Input clock 27 MHz

    input wire KEY0,            // Button 0 is reset

    output wire [3:0] VGA_R,

    output wire [3:0] VGA_G,

    output wire [3:0] VGA_B,

    output reg VGA_HS,

    output reg VGA_VS,

    output wire [21:0] FL_ADDR,

    input wire [7:0] FL_DQ,

    output wire FL_CE_N,

    output wire FL_OE_N,

    output wire FL_RST_N,

    output wire FL_WE_N,

    input wire PS2_CLK,

    input wire PS2_DAT,

    output wire UART_TXD,

    output wire [6:0] GPIO_0,   // Scope test points

    input wire SW0,

    input wire SW1,

    input wire SW2

);

`default_nettype none

//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

// Instantiate PLL and clocks block

//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

wire clk_pix;                   // VGA pixel clock (25.175 MHz)

wire clk_ula;                   // ULA master clock (14 MHz)

pll pll_( .inclk0(CLOCK_27), .c0(clk_pix), .c1(clk_ula) );

wire clk_cpu;                   // Clocks generates CPU clocks of 3.5 MHz

clocks clocks_( .* );

// Various scope test points, connect as needed:

//assign GPIO_0[0] = CLOCK_27;

//assign GPIO_0[1] = clk_pix;

//assign GPIO_0[2] = clk_ula;

//assign GPIO_0[3] = clk_cpu;

assign GPIO_0[4] = VGA_VS;

assign GPIO_0[5] = VGA_HS;

assign GPIO_0[6] = VGA_B[0];

assign GPIO_0[0] = PS2_CLK;

assign GPIO_0[1] = PS2_DAT;

assign GPIO_0[2] = UART_TXD;

assign GPIO_0[3] = vs_nintr;

//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

// Instantiate RAM that contains a sample screen image

//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

reg [12:0] vram_address;

reg [7:0] vram_data;

ram8 ram8_( .address(vram_address), .clock(clk_pix), .data(0), .wren(0), .q(vram_data));

//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

// State register containing the border color index

//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

reg [7:0] state;

// Testing: assign the border color index based on the board switches

wire [2:0] border;              // Border color index value

assign border = { SW2, SW1, SW0 };

//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

// Instantiate ULA's video subsystem

//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

wire vs_nintr;                  // Vertical retrace interrupt

video video_( .*, .vram_address(vram_address), .vram_data(vram_data) );

// Use flash interface instead of the internal RAM

assign FL_CE_N = 0;

assign FL_OE_N = 0;

assign FL_RST_N = KEY0;

assign FL_WE_N = 1;

assign FL_ADDR[21:13] = 'b10;

//video video_( .*, .vram_address(FL_ADDR[12:0]), .vram_data(FL_DQ) );

//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

// Instantiate keyboard support

//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

wire [7:0] scan_code;

wire scan_code_ready;

wire scan_code_error;

ps2_keyboard ps2_keyboard_( .*, .clk(CLOCK_50), .reset(KEY0) );

reg [15:0] A = 16'hFEFE;

wire [4:0] key_row;

zx_keyboard zx_keyboard_( .*, .clk(CLOCK_50), .reset(KEY0)  );

//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

// Add UART so we can echo keyboard through the serial port out

//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

wire busy_tx;

uart_core uart_core_( .*, .reset(!KEY0), .clk(CLOCK_50), .uart_tx(UART_TXD), .data_in(scan_code), .data_in_wr(scan_code_ready) );

endmodule