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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: template_periph_8b.v

// 

// *Module Description:

//                       8 bit peripheral template.

//

// *Author(s):

//              - Olivier Girard,    olgirard@gmail.com

//

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

`timescale 1ns / 100ps

module  template_periph_8b (

// OUTPUTs

    per_dout,                       // Peripheral data output

// 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

// 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          CNTRL1    = 9'h090;

parameter          CNTRL2    = 9'h091;

parameter          CNTRL3    = 9'h092;

parameter          CNTRL4    = 9'h093;

// Register one-hot decoder

parameter          CNTRL1_D  = (256'h1 << (CNTRL1 /2));

parameter          CNTRL2_D  = (256'h1 << (CNTRL2 /2));

parameter          CNTRL3_D  = (256'h1 << (CNTRL3 /2));

parameter          CNTRL4_D  = (256'h1 << (CNTRL4 /2));

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

// 2)  REGISTER DECODER

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

// Register address decode

reg  [255:0]  reg_dec;

always @(per_addr)

  case (per_addr)

    (CNTRL1 /2):   reg_dec   = CNTRL1_D;

    (CNTRL2 /2):   reg_dec   = CNTRL2_D;

    (CNTRL3 /2):   reg_dec   = CNTRL3_D;

    (CNTRL4 /2):   reg_dec   = CNTRL4_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

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

// CNTRL1 Register

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

reg  [7:0] cntrl1;

wire       cntrl1_wr  = CNTRL1[0] ? reg_hi_wr[CNTRL1/2] : reg_lo_wr[CNTRL1/2];

wire [7:0] cntrl1_nxt = CNTRL1[0] ? per_din[15:8]       : per_din[7:0];

always @ (posedge mclk or posedge puc)

  if (puc)            cntrl1 <=  8'h00;

  else if (cntrl1_wr) cntrl1 <=  cntrl1_nxt;

// CNTRL2 Register

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

reg  [7:0] cntrl2;

wire       cntrl2_wr  = CNTRL2[0] ? reg_hi_wr[CNTRL2/2] : reg_lo_wr[CNTRL2/2];

wire [7:0] cntrl2_nxt = CNTRL2[0] ? per_din[15:8]       : per_din[7:0];

always @ (posedge mclk or posedge puc)

  if (puc)            cntrl2 <=  8'h00;

  else if (cntrl2_wr) cntrl2 <=  cntrl2_nxt;

// CNTRL3 Register

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

reg  [7:0] cntrl3;

wire       cntrl3_wr  = CNTRL3[0] ? reg_hi_wr[CNTRL3/2] : reg_lo_wr[CNTRL3/2];

wire [7:0] cntrl3_nxt = CNTRL3[0] ? per_din[15:8]       : per_din[7:0];

always @ (posedge mclk or posedge puc)

  if (puc)            cntrl3 <=  8'h00;

  else if (cntrl3_wr) cntrl3 <=  cntrl3_nxt;

// CNTRL4 Register

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

reg  [7:0] cntrl4;

wire       cntrl4_wr  = CNTRL4[0] ? reg_hi_wr[CNTRL4/2] : reg_lo_wr[CNTRL4/2];

wire [7:0] cntrl4_nxt = CNTRL4[0] ? per_din[15:8]       : per_din[7:0];

always @ (posedge mclk or posedge puc)

  if (puc)            cntrl4 <=  8'h00;

  else if (cntrl4_wr) cntrl4 <=  cntrl4_nxt;

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

// 4) DATA OUTPUT GENERATION

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

// Data output mux

wire [15:0] cntrl1_rd   = (cntrl1  & {8{reg_rd[CNTRL1/2]}})  << (8 & {4{CNTRL1[0]}});

wire [15:0] cntrl2_rd   = (cntrl2  & {8{reg_rd[CNTRL2/2]}})  << (8 & {4{CNTRL2[0]}});

wire [15:0] cntrl3_rd   = (cntrl3  & {8{reg_rd[CNTRL3/2]}})  << (8 & {4{CNTRL3[0]}});

wire [15:0] cntrl4_rd   = (cntrl4  & {8{reg_rd[CNTRL4/2]}})  << (8 & {4{CNTRL4[0]}});

wire [15:0] per_dout  =  cntrl1_rd  |

                         cntrl2_rd  |

                         cntrl3_rd  |

                         cntrl4_rd;

endmodule // template_periph_8b