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[/] [sdr_ctrl/] [trunk/] [rtl/] [lib/] [sync_fifo.v] - Rev 31
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/********************************************************************* This file is part of the sdram controller project http://www.opencores.org/cores/sdr_ctrl/ Description: SYNC FIFO Parameters: W : Width (integer) D : Depth (integer, power of 2, 4 to 256) To Do: nothing Author(s): Dinesh Annayya, dinesha@opencores.org Copyright (C) 2000 Authors and OPENCORES.ORG 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, download it from http://www.opencores.org/lgpl.shtml *******************************************************************/ module sync_fifo (clk, reset_n, wr_en, wr_data, full, empty, rd_en, rd_data); parameter W = 8; parameter D = 4; parameter AW = (D == 4) ? 2 : (D == 8) ? 3 : (D == 16) ? 4 : (D == 32) ? 5 : (D == 64) ? 6 : (D == 128) ? 7 : (D == 256) ? 8 : 0; output [W-1 : 0] rd_data; input [W-1 : 0] wr_data; input clk, reset_n, wr_en, rd_en; output full, empty; // synopsys translate_off initial begin if (AW == 0) begin $display ("%m : ERROR!!! Fifo depth %d not in range 4 to 256", D); end // if (AW == 0) end // initial begin // synopsys translate_on reg [W-1 : 0] mem[D-1 : 0]; reg [AW-1 : 0] rd_ptr, wr_ptr; reg full, empty; wire [W-1 : 0] rd_data; always @ (posedge clk or negedge reset_n) if (reset_n == 1'b0) begin wr_ptr <= {AW{1'b0}} ; end else begin if (wr_en & !full) begin wr_ptr <= wr_ptr + 1'b1 ; end end always @ (posedge clk or negedge reset_n) if (reset_n == 1'b0) begin rd_ptr <= {AW{1'b0}} ; end else begin if (rd_en & !empty) begin rd_ptr <= rd_ptr + 1'b1 ; end end always @ (posedge clk or negedge reset_n) if (reset_n == 1'b0) begin empty <= 1'b1 ; end else begin empty <= (((wr_ptr - rd_ptr) == {{(AW-1){1'b0}}, 1'b1}) & rd_en & ~wr_en) ? 1'b1 : ((wr_ptr == rd_ptr) & ~rd_en & wr_en) ? 1'b0 : empty ; end always @ (posedge clk or negedge reset_n) if (reset_n == 1'b0) begin full <= 1'b0 ; end else begin full <= (((wr_ptr - rd_ptr) == {{(AW-1){1'b1}}, 1'b0}) & ~rd_en & wr_en) ? 1'b1 : (((wr_ptr - rd_ptr) == {AW{1'b1}}) & rd_en & ~wr_en) ? 1'b0 : full ; end always @ (posedge clk) if (wr_en) mem[wr_ptr] <= wr_data; assign rd_data = mem[rd_ptr]; // synopsys translate_off always @(posedge clk) begin if (wr_en && full) begin $display("%m : Error! sfifo overflow!"); end end always @(posedge clk) begin if (rd_en && empty) begin $display("%m : error! sfifo underflow!"); end end // synopsys translate_on //--------------------------------------- endmodule