OpenCores
URL https://opencores.org/ocsvn/versatile_mem_ctrl/versatile_mem_ctrl/trunk

Subversion Repositories versatile_mem_ctrl

Compare Revisions

  • This comparison shows the changes necessary to convert path 
    /versatile_mem_ctrl/trunk
    from Rev 84 to Rev 85
    ↔ Reverse comparison
  •

Rev 84 → Rev 85

/rtl/verilog/versatile_fifo_async_cmp.v
0,0 → 1,161
//////////////////////////////////////////////////////////////////////
//// ////
//// Versatile counter ////
//// ////
//// Description ////
//// Versatile counter, a reconfigurable binary, gray or LFSR ////
//// counter ////
//// ////
//// To Do: ////
//// - add LFSR with more taps ////
//// ////
//// Author(s): ////
//// - Michael Unneback, unneback@opencores.org ////
//// ORSoC AB ////
//// ////
//////////////////////////////////////////////////////////////////////
//// ////
//// Copyright (C) 2009 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 versatile_fifo_async_cmp ( wptr, rptr, fifo_empty, fifo_full, fifo_flag, wclk, rclk, rst );
 
parameter ADDR_WIDTH = 4;
parameter N = ADDR_WIDTH-1;
 
parameter Q1 = 2'b00;
parameter Q2 = 2'b01;
parameter Q3 = 2'b11;
parameter Q4 = 2'b10;
 
parameter going_empty = 1'b0;
parameter going_full = 1'b1;
 
parameter fifo_flag_value = 4'd4;
input [N:0] wptr, rptr;
output reg fifo_empty;
output fifo_full;
output fifo_flag;
input wclk, rclk, rst;
wire direction;
reg direction_set, direction_clr;
wire async_empty, async_full;
wire fifo_full2;
reg fifo_empty2;
reg [N:0] wptr1, wptr2, wptr_bin, rptr_bin;
reg [N:0] ptr_diff;
integer i;
// direction_set
always @ (wptr[N:N-1] or rptr[N:N-1])
case ({wptr[N:N-1],rptr[N:N-1]})
{Q1,Q2} : direction_set <= 1'b1;
{Q2,Q3} : direction_set <= 1'b1;
{Q3,Q4} : direction_set <= 1'b1;
{Q4,Q1} : direction_set <= 1'b1;
default : direction_set <= 1'b0;
endcase
 
// direction_clear
always @ (wptr[N:N-1] or rptr[N:N-1] or rst)
if (rst)
direction_clr <= 1'b1;
else
case ({wptr[N:N-1],rptr[N:N-1]})
{Q2,Q1} : direction_clr <= 1'b1;
{Q3,Q2} : direction_clr <= 1'b1;
{Q4,Q3} : direction_clr <= 1'b1;
{Q1,Q4} : direction_clr <= 1'b1;
default : direction_clr <= 1'b0;
endcase
 
`ifndef GENERATE_DIRECTION_AS_LATCH
dff_sr dff_sr_dir( .aclr(direction_clr), .aset(direction_set), .clock(1'b1), .data(1'b1), .q(direction));
`endif
 
`ifdef GENERATE_DIRECTION_AS_LATCH
always @ (posedge direction_set or posedge direction_clr)
if (direction_clr)
direction <= going_empty;
else
direction <= going_full;
`endif
 
assign async_empty = (wptr == rptr) && (direction==going_empty);
assign async_full = (wptr == rptr) && (direction==going_full);
 
dff_sr dff_sr_empty0( .aclr(rst), .aset(async_full), .clock(wclk), .data(async_full), .q(fifo_full2));
dff_sr dff_sr_empty1( .aclr(rst), .aset(async_full), .clock(wclk), .data(fifo_full2), .q(fifo_full));
 
/*
always @ (posedge wclk or posedge rst or posedge async_full)
if (rst)
{fifo_full, fifo_full2} <= 2'b00;
else if (async_full)
{fifo_full, fifo_full2} <= 2'b11;
else
{fifo_full, fifo_full2} <= {fifo_full2, async_full};
*/
always @ (posedge rclk or posedge async_empty)
if (async_empty)
{fifo_empty, fifo_empty2} <= 2'b11;
else
{fifo_empty,fifo_empty2} <= {fifo_empty2,async_empty};
 
 
// Write-domain to read-domain synchronizer
always @ (posedge rclk or posedge rst)
if (rst)
{wptr2,wptr1} <= {4'b0000,4'b0000};
else
{wptr2,wptr1} <= {wptr1,wptr};
 
// Gray-to-bin conversion
always @(wptr2)
for (i=0;i<4; i=i+1)
wptr_bin[i] = ^(wptr2>>i);
 
always @(rptr)
for (i=0;i<4; i=i+1)
rptr_bin[i] = ^(rptr>>i);
 
// Pointer difference
always @ (wptr_bin or rptr_bin)
if (wptr_bin > rptr_bin)
ptr_diff <= wptr_bin - rptr_bin;
else if (wptr_bin < rptr_bin)
ptr_diff <= ((5'd16 - rptr_bin) + wptr_bin);
else
ptr_diff <= 4'd0;
 
// Flag
assign fifo_flag = (ptr_diff >= fifo_flag_value);
endmodule // async_comp

powered by: WebSVN 2.1.0

© copyright 1999-2024 OpenCores.org, equivalent to Oliscience, all rights reserved. OpenCores®, registered trademark.