1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
|
// -*- verilog -*-
//
// USRP - Universal Software Radio Peripheral
//
// Copyright (C) 2003 Matt Ettus
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// This program 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 General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Boston, MA 02110-1301 USA
//
// Vendor Independent FIFO module
// Width and Depth should be parameterizable
// Asynchronous clocks for each side
// Read side is read-acknowledge, not read-request
// FIFO does not enforce "don't write when full, don't read when empty"
// That is up to the connecting modules
// The FIFO only holds 2^N-1 entries, not 2^N
module fifo (reset,data,write,wrclk,wr_used,q,read_ack,rdclk,rd_used);
parameter width=32;
parameter depth=10;
input reset; // Asynchronous
input [width-1:0] data;
input write;
input wrclk;
output [depth-1:0] wr_used;
output [width-1:0] q;
input read_ack;
input rdclk;
output [depth-1:0] rd_used;
reg [depth-1:0] read_addr, write_addr,
read_addr_gray, read_addr_gray_sync,
write_addr_gray, write_addr_gray_sync;
// Pseudo-dual-port RAM
dpram #(.depth(10),.width(width),.size(1024))
fifo_ram (.wclk(wrclk),.wdata(data),.waddr(write_addr),.wen(write),
.rclk(rdclk), .rdata(q),.raddr(read_addr) );
wire [depth-1:0] wag,rag;
// Keep track of own side's pointer
always @(posedge wrclk or posedge reset)
if(reset) write_addr <= #1 0;
else if(write) write_addr <= #1 write_addr + 1;
always @(posedge rdclk or posedge reset)
if(reset) read_addr <= #1 0;
else if(read_ack) read_addr <= #1 read_addr + 1;
// Convert own side pointer to gray
bin2gray #(depth) write_b2g (write_addr,wag);
bin2gray #(depth) read_b2g (read_addr,rag);
// Latch it
always @(posedge wrclk or posedge reset)
if(reset) write_addr_gray <= #1 0;
else write_addr_gray <= #1 wag;
always @(posedge rdclk or posedge reset)
if(reset) read_addr_gray <= #1 0;
else read_addr_gray <= #1 rag;
// Send it to other side and latch
always @(posedge wrclk or posedge reset)
if(reset) read_addr_gray_sync <= #1 0;
else read_addr_gray_sync <= #1 read_addr_gray;
always @(posedge rdclk or posedge reset)
if(reset) write_addr_gray_sync <= #1 0;
else write_addr_gray_sync <= #1 write_addr_gray;
wire [depth-1:0] write_addr_sync, read_addr_sync;
// Convert back to binary
gray2bin #(depth) write_g2b (write_addr_gray_sync, write_addr_sync);
gray2bin #(depth) read_g2b (read_addr_gray_sync, read_addr_sync);
assign rd_used = write_addr_sync - read_addr;
assign wr_used = write_addr - read_addr_sync;
endmodule // fifo
module bin2gray(bin_val,gray_val);
parameter width = 8;
input [width-1:0] bin_val;
output reg [width-1:0] gray_val;
integer i;
always @*
begin
gray_val[width-1] = bin_val[width-1];
for(i=0;i<width-1;i=i+1)
gray_val[i] = bin_val[i] ^ bin_val[i+1];
end
endmodule // bin2gray
module gray2bin(gray_val,bin_val);
parameter width = 8;
input [width-1:0] gray_val;
output reg [width-1:0] bin_val;
integer i;
always @*
begin
bin_val[width-1] = gray_val[width-1];
for(i=width-2;i>=0;i=i-1)
bin_val[i] = bin_val[i+1] ^ gray_val[i];
end
endmodule // gray2bin
|
