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//----------------------------------------------------------------------------

// Copyright (C) 2001 Authors

//

// This source file may be used and distributed without restriction provided

// that this copyright statement is not removed from the file and that any

// derivative work contains the original copyright notice and the associated

// disclaimer.

//

// This source file is free software; you can redistribute it and/or modify

// it under the terms of the GNU Lesser General Public License as published

// by the Free Software Foundation; either version 2.1 of the License, or

// (at your option) any later version.

//

// This source 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 Lesser General Public

// License for more details.

//

// You should have received a copy of the GNU Lesser General Public License

// along with this source; if not, write to the Free Software Foundation,

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

//

//----------------------------------------------------------------------------

//

// *File Name: driver_7segment.v

// 

// *Module Description:

//                      Driver for the four-digit, seven-segment LED display.

//

// *Author(s):

//              - Olivier Girard,    olgirard@gmail.com

//

//----------------------------------------------------------------------------

`timescale 1ns / 100ps

module  driver_7segment (

// OUTPUTs

    per_dout,                       // Peripheral data output

    seg_a,                          // Segment A control

    seg_b,                          // Segment B control

    seg_c,                          // Segment C control

    seg_d,                          // Segment D control

    seg_e,                          // Segment E control

    seg_f,                          // Segment F control

    seg_g,                          // Segment G control

    seg_dp,                         // Segment DP control

    seg_an0,                        // Anode 0 control

    seg_an1,                        // Anode 1 control

    seg_an2,                        // Anode 2 control

    seg_an3,                        // Anode 3 control

// INPUTs

    mclk,                           // Main system clock

    per_addr,                       // Peripheral address

    per_din,                        // Peripheral data input

    per_en,                         // Peripheral enable (high active)

    per_wen,                        // Peripheral write enable (high active)

    puc                             // Main system reset

);

// OUTPUTs

//=========

output      [15:0] per_dout;        // Peripheral data output

output             seg_a;           // Segment A control

output             seg_b;           // Segment B control

output             seg_c;           // Segment C control

output             seg_d;           // Segment D control

output             seg_e;           // Segment E control

output             seg_f;           // Segment F control

output             seg_g;           // Segment G control

output             seg_dp;          // Segment DP control

output             seg_an0;         // Anode 0 control

output             seg_an1;         // Anode 1 control

output             seg_an2;         // Anode 2 control

output             seg_an3;         // Anode 3 control

// INPUTs

//=========

input              mclk;            // Main system clock

input        [7:0] per_addr;        // Peripheral address

input       [15:0] per_din;         // Peripheral data input

input              per_en;          // Peripheral enable (high active)

input        [1:0] per_wen;         // Peripheral write enable (high active)

input              puc;             // Main system reset

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

// 1)  PARAMETER DECLARATION

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

// Register addresses

parameter          DIGIT0    = 9'h090;

parameter          DIGIT1    = 9'h091;

parameter          DIGIT2    = 9'h092;

parameter          DIGIT3    = 9'h093;

// Register one-hot decoder

parameter          DIGIT0_D  = (256'h1 << (DIGIT0 /2));

parameter          DIGIT1_D  = (256'h1 << (DIGIT1 /2));

parameter          DIGIT2_D  = (256'h1 << (DIGIT2 /2));

parameter          DIGIT3_D  = (256'h1 << (DIGIT3 /2));

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

// 2)  REGISTER DECODER

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

// Register address decode

reg  [255:0]  reg_dec;

always @(per_addr)

  case (per_addr)

    (DIGIT0 /2):   reg_dec   = DIGIT0_D;

    (DIGIT1 /2):   reg_dec   = DIGIT1_D;

    (DIGIT2 /2):   reg_dec   = DIGIT2_D;

    (DIGIT3 /2):   reg_dec   = DIGIT3_D;

    default    :   reg_dec   = {256{1'b0}};

  endcase

// Read/Write probes

wire         reg_lo_write =  per_wen[0] & per_en;

wire         reg_hi_write =  per_wen[1] & per_en;

wire         reg_read     = ~|per_wen   & per_en;

// Read/Write vectors

wire [255:0] reg_hi_wr    = reg_dec & {256{reg_hi_write}};

wire [255:0] reg_lo_wr    = reg_dec & {256{reg_lo_write}};

wire [255:0] reg_rd       = reg_dec & {256{reg_read}};

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

// 3) REGISTERS

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

// DIGIT0 Register

//-----------------

reg  [7:0] digit0;

wire       digit0_wr  = DIGIT0[0] ? reg_hi_wr[DIGIT0/2] : reg_lo_wr[DIGIT0/2];

wire [7:0] digit0_nxt = DIGIT0[0] ? per_din[15:8]       : per_din[7:0];

always @ (posedge mclk or posedge puc)

  if (puc)            digit0 <=  8'h00;

  else if (digit0_wr) digit0 <=  digit0_nxt;

// DIGIT1 Register

//-----------------

reg  [7:0] digit1;

wire       digit1_wr  = DIGIT1[0] ? reg_hi_wr[DIGIT1/2] : reg_lo_wr[DIGIT1/2];

wire [7:0] digit1_nxt = DIGIT1[0] ? per_din[15:8]       : per_din[7:0];

always @ (posedge mclk or posedge puc)

  if (puc)            digit1 <=  8'h00;

  else if (digit1_wr) digit1 <=  digit1_nxt;

// DIGIT2 Register

//-----------------

reg  [7:0] digit2;

wire       digit2_wr  = DIGIT2[0] ? reg_hi_wr[DIGIT2/2] : reg_lo_wr[DIGIT2/2];

wire [7:0] digit2_nxt = DIGIT2[0] ? per_din[15:8]       : per_din[7:0];

always @ (posedge mclk or posedge puc)

  if (puc)            digit2 <=  8'h00;

  else if (digit2_wr) digit2 <=  digit2_nxt;

// DIGIT3 Register

//-----------------

reg  [7:0] digit3;

wire       digit3_wr  = DIGIT3[0] ? reg_hi_wr[DIGIT3/2] : reg_lo_wr[DIGIT3/2];

wire [7:0] digit3_nxt = DIGIT3[0] ? per_din[15:8]       : per_din[7:0];

always @ (posedge mclk or posedge puc)

  if (puc)            digit3 <=  8'h00;

  else if (digit3_wr) digit3 <=  digit3_nxt;

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

// 4) DATA OUTPUT GENERATION

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

// Data output mux

wire [15:0] digit0_rd   = (digit0  & {8{reg_rd[DIGIT0/2]}})  << (8 & {4{DIGIT0[0]}});

wire [15:0] digit1_rd   = (digit1  & {8{reg_rd[DIGIT1/2]}})  << (8 & {4{DIGIT1[0]}});

wire [15:0] digit2_rd   = (digit2  & {8{reg_rd[DIGIT2/2]}})  << (8 & {4{DIGIT2[0]}});

wire [15:0] digit3_rd   = (digit3  & {8{reg_rd[DIGIT3/2]}})  << (8 & {4{DIGIT3[0]}});

wire [15:0] per_dout  =  digit0_rd  |

                         digit1_rd  |

                         digit2_rd  |

                         digit3_rd;

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

// 5) FOUR-DIGIT, SEVEN-SEGMENT LED DISPLAY DRIVER

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

// Anode selection

//------------------

// Free running counter

reg [23:0] anode_cnt;

always @ (posedge mclk or posedge puc)

if (puc) anode_cnt <=  24'h00_0000;

else     anode_cnt <=  anode_cnt+24'h00_0001;

// Anode selection

wire [3:0] seg_an  = (4'h1 << anode_cnt[17:16]);

wire       seg_an0 = ~seg_an[0];

wire       seg_an1 = ~seg_an[1];

wire       seg_an2 = ~seg_an[2];

wire       seg_an3 = ~seg_an[3];

// Segment selection

//----------------------------

wire [7:0] digit  = seg_an[0] ? digit0 :

                    seg_an[1] ? digit1 :

                    seg_an[2] ? digit2 :

                                digit3;

wire       seg_a  = ~digit[7];

wire       seg_b  = ~digit[6];

wire       seg_c  = ~digit[5];

wire       seg_d  = ~digit[4];

wire       seg_e  = ~digit[3];

wire       seg_f  = ~digit[2];

wire       seg_g  = ~digit[1];

wire       seg_dp = ~digit[0];

endmodule // driver_7segment