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/*

        1942 simple board setup in order to test SQMUSIC.

        Requirements:

                  TV80, Z80 Verilog module

                        Dump of Z80 ROM from 1942 board

  (c) Jose Tejada Gomez, 9th May 2013

  You can use this file following the GNU GENERAL PUBLIC LICENSE version 3

  Read the details of the license in:

  http://www.gnu.org/licenses/gpl.txt

  Send comments to: jose.tejada@ieee.org

*/

module computer_1942

#(parameter dump_regs=0) // set to 1 to dump sqmusic registers

(

  input clk,

        input sound_clk,

        input reset_n,

        input int_n,

        output [3:0] ay0_a,

        output [3:0] ay0_b,

        output [3:0] ay0_c,

        output [3:0] ay1_a,

        output [3:0] ay1_b,

        output [3:0] ay1_c,

        output bus_error

);

  reg wait_n, nmi_n, busrq_n;

  wire [7:0]cpu_in, cpu_out;

  wire [15:0]adr;

  wire m1_n, mreq_n, iorq_n, rd_n, wr_n, rfsh_n, halt_n, busak_n;

  wire bus_error;

//      wire [15:0] amp0_y, amp1_y;

  wire [7:0]ram_out, rom_out, latch_out;

  wire rom_enable = adr<16'h4000 ? 1:0;

  wire ram_enable = adr>=16'h4000 && adr<16'h4800 ? 1:0;

  wire latch_enable = adr==16'h6000 ? 1 : 0;

  wire ay_0_enable = adr==16'h8000 || adr==16'h8001 ? 1:0;

  wire ay_1_enable = adr==16'hC000 || adr==16'hC001 ? 1:0;

  assign bus_error = ~ram_enable & ~rom_enable & ~latch_enable &

    ~ay_0_enable & ~ay_1_enable;

  assign cpu_in=ram_out | rom_out | latch_out;

/*

        always @(negedge rd_n)

                if( !rd_n       && adr==8'h38 )

                        $display("IRQ processing started @ %t us",$time/1e6);

*/

  initial begin

    nmi_n=1;

    wait_n=1;

  end

  tv80n cpu( //outputs

  .m1_n(m1_n), .mreq_n(mreq_n), .iorq_n(iorq_n), .rd_n(rd_n), .wr_n(wr_n),

  .rfsh_n(rfsh_n), .halt_n(halt_n), .busak_n(busak_n), .A(adr), .do(cpu_out),

  // Inputs

  .reset_n(reset_n), .clk(clk), .wait_n(wait_n),

  .int_n(int_n), .nmi_n(nmi_n), .busrq_n(busrq_n), .di(cpu_in) );

  RAM ram(.adr(adr[10:0]), .din(cpu_out), .dout(ram_out), .enable( ram_enable ),

    .clk(clk), .wr_n(wr_n), .rd_n(rd_n) );

  ROM rom(.adr(adr[13:0]), .data(rom_out), .enable(rom_enable),

   .rd_n(rd_n), .clk(clk));

  SOUND_LATCH sound_latch( .dout(latch_out), .enable(latch_enable),

    .clk(clk), .rd_n(rd_n) );

//      fake_ay ay_0( .adr(adr[0]), .din(din), .clk(clk), .wr_n(~ay_0_enable|wr_n) );

        AY_3_8910_capcom #(dump_regs,0) ay_0( .reset_n(reset_n), .clk(clk), .sound_clk(sound_clk),

                .din(cpu_out), .adr(adr[0]), .wr_n(wr_n), .cs_n(~ay_0_enable),

                .A(ay0_a), .B(ay0_b), .C(ay0_c) );

        AY_3_8910_capcom #(dump_regs,1) ay_1( .reset_n(reset_n), .clk(clk), .sound_clk(sound_clk),

                .din(cpu_out), .adr(adr[0]), .wr_n(wr_n), .cs_n(~ay_1_enable),

                .A(ay1_a), .B(ay1_b), .C(ay1_c) );

endmodule

//////////////////////////////////////////////////////////

// this module is used to check the communication of the

// Z80 with the AY-3-8910

// only used for debugging

module fake_ay(

        input adr,

  input [7:0] din,

  input clk,

  input wr_n );

        reg [7:0] contents[1:0];

        wire sample = clk & ~wr_n;

        always @(posedge sample) begin

//              if( contents[adr] != din ) begin

                $display("%t -> %d = %d", $realtime/1e6, adr, din );

                if( !adr && din>15 ) $display("AY WARNING");

                contents[adr] = din;

        end

endmodule

//////////////////////////////////////////////////////////

module RAM(

  input [10:0] adr,

  input [7:0] din,

  output reg [7:0] dout,

  input enable,

  input clk,

  input rd_n,

  input wr_n );

reg [7:0] contents[2047:0];

wire sample = clk & (~rd_n | ~wr_n );

initial dout=0;

always @(posedge sample) begin

  if( !enable )

    dout=0;

  else begin

    if( !wr_n ) contents[adr]=din;

    if( !rd_n ) dout=contents[adr];

  end

end

endmodule

//////////////////////////////////////////////////////////

module ROM(

  input  [13:0] adr,

  output reg [7:0] data,

  input enable,

  input rd_n,

  input clk );

reg [7:0] contents[16383:0];

wire sample = clk & ~rd_n;

initial begin

  $readmemh("../rom/sr-01.c11.hex", contents ); // this is the hex dump of the ROM

  data=0;

end

always @( posedge sample ) begin

  if ( !enable )

    data=0;

  else

    data=contents[ adr ];

end

endmodule

//////////////////////////////////////////////////////////

module SOUND_LATCH(

  output reg [7:0] dout,

  input enable,

  input clk,

  input rd_n );

wire sample = clk & ~rd_n;

reg [7:0]data;

initial begin

        dout=0;

        data=0;

        #100e6 data=8'h12; // enter the song/sound code here

end

always @(posedge sample) begin

  if( !enable )

                dout=0;

  else begin

    if( !rd_n ) begin

                        // $display("Audio latch read @ %t us", $realtime/1e6 );

//                      if( data != 0 ) 

//                        $display("Audio latch read (%X) @ %t us", data, $realtime/1e6 );

                        dout=data;

                end

  end

end

endmodule