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

// Copyright (C) 2009 , Olivier Girard

//

// Redistribution and use in source and binary forms, with or without

// modification, are permitted provided that the following conditions

// are met:

//     * Redistributions of source code must retain the above copyright

//       notice, this list of conditions and the following disclaimer.

//     * Redistributions in binary form must reproduce the above copyright

//       notice, this list of conditions and the following disclaimer in the

//       documentation and/or other materials provided with the distribution.

//     * Neither the name of the authors nor the names of its contributors

//       may be used to endorse or promote products derived from this software

//       without specific prior written permission.

//

// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"

// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE

// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,

// OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS

// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN

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// THE POSSIBILITY OF SUCH DAMAGE

//

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

//

// *File Name: template_periph_8b.v

// 

// *Module Description:

//                       8 bit peripheral template.

//

// *Author(s):

//              - Olivier Girard,    olgirard@gmail.com

//

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

// $Rev: 134 $

// $LastChangedBy: olivier.girard $

// $LastChangedDate: 2012-03-22 21:31:06 +0100 (Thu, 22 Mar 2012) $

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

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_we,                         // Peripheral write enable (high active)

    puc_rst                         // Main system reset

);

// OUTPUTs

//=========

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

// INPUTs

//=========

input              mclk;            // Main system clock

input       [13:0] per_addr;        // Peripheral address

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

input              per_en;          // Peripheral enable (high active)

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

input              puc_rst;         // Main system reset

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

// 1)  PARAMETER DECLARATION

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

// Register base address (must be aligned to decoder bit width)

parameter       [14:0] BASE_ADDR   = 15'h0090;

// Decoder bit width (defines how many bits are considered for address decoding)

parameter              DEC_WD      =  2;

// Register addresses offset

parameter [DEC_WD-1:0] CNTRL1      =  'h0,

                       CNTRL2      =  'h1,

                       CNTRL3      =  'h2,

                       CNTRL4      =  'h3;

// Register one-hot decoder utilities

parameter              DEC_SZ      =  (1 << DEC_WD);

parameter [DEC_SZ-1:0] BASE_REG    =  {{DEC_SZ-1{1'b0}}, 1'b1};

// Register one-hot decoder

parameter [DEC_SZ-1:0] CNTRL1_D  = (BASE_REG << CNTRL1),

                       CNTRL2_D  = (BASE_REG << CNTRL2),

                       CNTRL3_D  = (BASE_REG << CNTRL3),

                       CNTRL4_D  = (BASE_REG << CNTRL4);

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

// 2)  REGISTER DECODER

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

// Local register selection

wire              reg_sel      =  per_en & (per_addr[13:DEC_WD-1]==BASE_ADDR[14:DEC_WD]);

// Register local address

wire [DEC_WD-1:0] reg_addr     =  {1'b0, per_addr[DEC_WD-2:0]};

// Register address decode

wire [DEC_SZ-1:0] reg_dec      = (CNTRL1_D  &  {DEC_SZ{(reg_addr==(CNTRL1 >>1))}}) |

                                 (CNTRL2_D  &  {DEC_SZ{(reg_addr==(CNTRL2 >>1))}}) |

                                 (CNTRL3_D  &  {DEC_SZ{(reg_addr==(CNTRL3 >>1))}}) |

                                 (CNTRL4_D  &  {DEC_SZ{(reg_addr==(CNTRL4 >>1))}});

// Read/Write probes

wire              reg_lo_write =  per_we[0] & reg_sel;

wire              reg_hi_write =  per_we[1] & reg_sel;

wire              reg_read     = ~|per_we   & reg_sel;

// Read/Write vectors

wire [DEC_SZ-1:0] reg_hi_wr    = reg_dec & {DEC_SZ{reg_hi_write}};

wire [DEC_SZ-1:0] reg_lo_wr    = reg_dec & {DEC_SZ{reg_lo_write}};

wire [DEC_SZ-1:0] reg_rd       = reg_dec & {DEC_SZ{reg_read}};

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

// 3) REGISTERS

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

// CNTRL1 Register

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

reg  [7:0] cntrl1;

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

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

always @ (posedge mclk or posedge puc_rst)

  if (puc_rst)        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] : reg_lo_wr[CNTRL2];

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

always @ (posedge mclk or posedge puc_rst)

  if (puc_rst)        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] : reg_lo_wr[CNTRL3];

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

always @ (posedge mclk or posedge puc_rst)

  if (puc_rst)        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] : reg_lo_wr[CNTRL4];

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

always @ (posedge mclk or posedge puc_rst)

  if (puc_rst)        cntrl4 <=  8'h00;

  else if (cntrl4_wr) cntrl4 <=  cntrl4_nxt;

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

// 4) DATA OUTPUT GENERATION

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

// Data output mux

wire [15:0] cntrl1_rd   = {8'h00, (cntrl1  & {8{reg_rd[CNTRL1]}})}  << (8 & {4{CNTRL1[0]}});

wire [15:0] cntrl2_rd   = {8'h00, (cntrl2  & {8{reg_rd[CNTRL2]}})}  << (8 & {4{CNTRL2[0]}});

wire [15:0] cntrl3_rd   = {8'h00, (cntrl3  & {8{reg_rd[CNTRL3]}})}  << (8 & {4{CNTRL3[0]}});

wire [15:0] cntrl4_rd   = {8'h00, (cntrl4  & {8{reg_rd[CNTRL4]}})}  << (8 & {4{CNTRL4[0]}});

wire [15:0] per_dout  =  cntrl1_rd  |

                         cntrl2_rd  |

                         cntrl3_rd  |

                         cntrl4_rd;

endmodule // template_periph_8b