Subversion Repositories opengfx430

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

// Copyright (C) 2015 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: ogfx_backend_lut_fifo.v

//

// *Module Description:

//                      Simple FIFO module

//

// *Author(s):

//              - Olivier Girard,    olgirard@gmail.com

//

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

// $Rev$

// $LastChangedBy$

// $LastChangedDate$

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

`ifdef OGFX_NO_INCLUDE

`else

`include "openGFX430_defines.v"

`endif

module  ogfx_reg_fifo (

// OUTPUTs

    fifo_cnt_o,                         // Fifo counter

    fifo_data_o,                        // Read data output

    fifo_done_evt_o,                    // Fifo has been emptied

    fifo_empty_o,                       // Fifo is currentely empty

    fifo_full_o,                        // Fifo is currentely full

    fifo_ovfl_evt_o,                    // Fifo overflow event

// INPUTs

    mclk,                               // Main system clock

    puc_rst,                            // Main system reset

    fifo_data_i,                        // Read data input

    fifo_enable_i,                      // Enable fifo (flushed when disabled)

    fifo_pop_i,                         // Pop data from the fifo

    fifo_push_i                         // Push new data to the fifo

);

// OUTPUTs

//=========

output         [3:0] fifo_cnt_o;        // Fifo counter

output        [15:0] fifo_data_o;       // Read data output

output               fifo_done_evt_o;   // Fifo has been emptied

output               fifo_empty_o;      // Fifo is currentely empty

output               fifo_full_o;       // Fifo is currentely full

output               fifo_ovfl_evt_o;   // Fifo overflow event

// INPUTs

//=========

input                mclk;              // Main system clock

input                puc_rst;           // Main system reset

input         [15:0] fifo_data_i;       // Read data input

input                fifo_enable_i;     // Enable fifo (flushed when disabled)

input                fifo_pop_i;        // Pop data from the fifo

input                fifo_push_i;       // Push new data to the fifo

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

// 1)  WIRE, REGISTERS AND PARAMETER DECLARATION

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

// Some parameter(s)

parameter    FIFO_EMPTY        =  4'h0,

             FIFO_FULL         =  4'hf;

// Others

reg    [3:0] fifo_cnt_o;

wire   [3:0] fifo_cnt_nxt;

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

// 5) FIFO COUNTER

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

// Control signals

wire      fifo_full_o     =  (fifo_cnt_o == FIFO_FULL);

wire      fifo_empty_o    =  (fifo_cnt_o == FIFO_EMPTY);

wire      fifo_push_int   =  fifo_push_i & !fifo_full_o;

wire      fifo_pop_int    =  fifo_pop_i  & !fifo_empty_o;

// Events

assign    fifo_done_evt_o = ~fifo_empty_o & (fifo_cnt_nxt == FIFO_EMPTY);

assign    fifo_ovfl_evt_o =  fifo_push_i  &  fifo_full_o;

// Fifo counter

assign fifo_cnt_nxt = ~fifo_enable_i                 ?  FIFO_EMPTY        : // Initialize

                      (fifo_push_int & fifo_pop_int) ?  fifo_cnt_o        : // Keep value (pop & push at the same time)

                       fifo_push_int                 ?  fifo_cnt_o + 3'h1 : // Push

                       fifo_pop_int                  ?  fifo_cnt_o - 3'h1 : // Pop

                                                        fifo_cnt_o;         // Hold

always @(posedge mclk or posedge puc_rst)

  if (puc_rst) fifo_cnt_o <= FIFO_EMPTY;

  else         fifo_cnt_o <= fifo_cnt_nxt;

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

// 6) FIFO MEMORY & RD/WR POINTERS

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

// Write pointer

reg [3:0] wr_ptr;

always @(posedge mclk or posedge puc_rst)

  if (puc_rst)                    wr_ptr  <=  4'h0;

  else if (~fifo_enable_i)        wr_ptr  <=  4'h0;

  else if (fifo_push_int)

    begin

       if (wr_ptr==(FIFO_FULL-1)) wr_ptr  <=  4'h0;

       else                       wr_ptr  <=  wr_ptr + 4'h1;

    end

// Memory

reg [15:0] fifo_mem [0:15];

always @(posedge mclk or posedge puc_rst)

  if (puc_rst)

    begin

       fifo_mem[0]      <=  16'h0000;

       fifo_mem[1]      <=  16'h0000;

       fifo_mem[2]      <=  16'h0000;

       fifo_mem[3]      <=  16'h0000;

       fifo_mem[4]      <=  16'h0000;

       fifo_mem[5]      <=  16'h0000;

       fifo_mem[6]      <=  16'h0000;

       fifo_mem[7]      <=  16'h0000;

       fifo_mem[8]      <=  16'h0000;

       fifo_mem[9]      <=  16'h0000;

       fifo_mem[10]     <=  16'h0000;

       fifo_mem[11]     <=  16'h0000;

       fifo_mem[12]     <=  16'h0000;

       fifo_mem[13]     <=  16'h0000;

       fifo_mem[14]     <=  16'h0000;

       fifo_mem[15]     <=  16'h0000;

    end

  else if (fifo_push_int)

    begin

       fifo_mem[wr_ptr] <=  fifo_data_i;

    end

// Read pointer

reg [3:0] rd_ptr;

always @(posedge mclk or posedge puc_rst)

  if (puc_rst)                    rd_ptr  <=  4'h0;

  else if (~fifo_enable_i)        rd_ptr  <=  4'h0;

  else if (fifo_pop_int)

    begin

       if (rd_ptr==(FIFO_FULL-1)) rd_ptr  <=  4'h0;

       else                       rd_ptr  <=  rd_ptr + 4'h1;

    end

assign fifo_data_o = fifo_mem[rd_ptr];

endmodule // ogfx_reg_fifo

`ifdef OGFX_NO_INCLUDE

`else

`include "openGFX430_undefines.v"

`endif