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1 | // ========== Copyright Header Begin ========================================== |
2 | // | |
3 | // OpenSPARC T2 Processor File: dmu_common_simple_fifo.v | |
4 | // Copyright (C) 1995-2007 Sun Microsystems, Inc. All Rights Reserved | |
5 | // 4150 Network Circle, Santa Clara, California 95054, U.S.A. | |
6 | // | |
7 | // * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | |
8 | // | |
9 | // This program is free software; you can redistribute it and/or modify | |
10 | // it under the terms of the GNU General Public License as published by | |
11 | // the Free Software Foundation; version 2 of the License. | |
12 | // | |
13 | // This program is distributed in the hope that it will be useful, | |
14 | // but WITHOUT ANY WARRANTY; without even the implied warranty of | |
15 | // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
16 | // GNU General Public License for more details. | |
17 | // | |
18 | // You should have received a copy of the GNU General Public License | |
19 | // along with this program; if not, write to the Free Software | |
20 | // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA | |
21 | // | |
22 | // For the avoidance of doubt, and except that if any non-GPL license | |
23 | // choice is available it will apply instead, Sun elects to use only | |
24 | // the General Public License version 2 (GPLv2) at this time for any | |
25 | // software where a choice of GPL license versions is made | |
26 | // available with the language indicating that GPLv2 or any later version | |
27 | // may be used, or where a choice of which version of the GPL is applied is | |
28 | // otherwise unspecified. | |
29 | // | |
30 | // Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, | |
31 | // CA 95054 USA or visit www.sun.com if you need additional information or | |
32 | // have any questions. | |
33 | // | |
34 | // ========== Copyright Header End ============================================ | |
35 | module dmu_common_simple_fifo ( | |
36 | clk, | |
37 | rst_l, | |
38 | ||
39 | data_in, | |
40 | write, | |
41 | ||
42 | data_out, | |
43 | read, | |
44 | ||
45 | fifo_full, | |
46 | fifo_almost_full, | |
47 | fifo_empty | |
48 | ||
49 | ); | |
50 | ||
51 | ||
52 | //############################################################################ | |
53 | // PARAMETERS | |
54 | //############################################################################ | |
55 | parameter FIFO_WIDTH = 131; | |
56 | parameter FIFO_DEPTH = 4'd8; | |
57 | parameter FIFO_PTR_WDTH = 3; | |
58 | parameter FIFO_DEPTH_MINUS_ONE = 3'd7; | |
59 | ||
60 | ||
61 | //############################################################################ | |
62 | // PORT DECLARATIONS | |
63 | //############################################################################ | |
64 | ||
65 | input clk; // The input clock | |
66 | input rst_l; // The fifo rst_l | |
67 | ||
68 | input [FIFO_WIDTH - 1:0] data_in; // The input data | |
69 | input write; // The syncronous write strobe | |
70 | ||
71 | output [FIFO_WIDTH - 1:0] data_out; // The output data | |
72 | input read; // The syncronous read strobe | |
73 | ||
74 | output fifo_full; // The fifo full flag | |
75 | output fifo_almost_full; // The fifo almost full flag (full -1) | |
76 | output fifo_empty; // The fifo empty flag | |
77 | ||
78 | ||
79 | //############################################################################ | |
80 | // SIGNAL DECLARATIONS | |
81 | //############################################################################ | |
82 | ||
83 | //************************************************** | |
84 | // Registers that Are Flops | |
85 | //************************************************** | |
86 | reg [FIFO_WIDTH - 1:0] fifo_ram[0:FIFO_DEPTH -1]; // The fifo storge arrary | |
87 | reg [FIFO_PTR_WDTH - 1:0] wr_ptr, rd_ptr; // Read and write pointers | |
88 | reg [FIFO_PTR_WDTH:0] fifo_count; // Number of entries in fifo | |
89 | reg over_flow_err, under_flow_err; // Under flow and over flow errors | |
90 | ||
91 | ||
92 | //************************************************** | |
93 | // Registers that Are NOT Flops | |
94 | //************************************************** | |
95 | reg [FIFO_PTR_WDTH:0] n_fifo_count; // Next Number of entries in fifo | |
96 | reg n_over_flow_err, n_under_flow_err; // Next Under flow and over flow errors | |
97 | ||
98 | //************************************************** | |
99 | // Wires | |
100 | //************************************************** | |
101 | wire [FIFO_PTR_WDTH - 1:0] n_wr_ptr, n_rd_ptr; // Next Read and write pointers | |
102 | wire fifo_full, fifo_empty; // Full and empty signals | |
103 | ||
104 | wire [FIFO_WIDTH - 1:0] data_out; | |
105 | ||
106 | //############################################################################ | |
107 | // ZERO IN CHECKERS | |
108 | //############################################################################ | |
109 | ||
110 | // A fifo checker for this fifo | |
111 | ||
112 | //0in fifo -enq write -deq read -depth FIFO_DEPTH -enq_data data_in -deq_data data_out | |
113 | ||
114 | // *********************************************** | |
115 | // If this is a write access, put the data on the | |
116 | // input bus into the location pointed to by the | |
117 | // fifo write pointer | |
118 | //************************************************ | |
119 | always @ (posedge clk) | |
120 | if(~rst_l) begin : fifo_rst | |
121 | integer j; | |
122 | for (j = 0; j < FIFO_DEPTH; j = j + 1) begin | |
123 | fifo_ram[j] <= {FIFO_WIDTH{1'b0}}; | |
124 | end | |
125 | end | |
126 | else begin | |
127 | if (write) begin | |
128 | fifo_ram[wr_ptr] <= data_in; | |
129 | end | |
130 | end | |
131 | ||
132 | //*********************************************** | |
133 | // If this is a read get the data that is in | |
134 | // the location pointed to by the read pointer | |
135 | // and put it onto the output bus | |
136 | //************************************************ | |
137 | ||
138 | assign data_out = fifo_ram[rd_ptr]; | |
139 | ||
140 | ||
141 | //************************************************ | |
142 | // Increment the write pointer on every write and | |
143 | // the read pointer on every read | |
144 | //************************************************/ | |
145 | always @ (posedge clk) | |
146 | if (!rst_l) | |
147 | begin | |
148 | wr_ptr <= 0; | |
149 | rd_ptr <= 0; | |
150 | end | |
151 | else | |
152 | begin | |
153 | wr_ptr <= n_wr_ptr; | |
154 | rd_ptr <= n_rd_ptr; | |
155 | end | |
156 | ||
157 | assign n_wr_ptr = write ? ((wr_ptr == FIFO_DEPTH_MINUS_ONE) ? 0 : (wr_ptr + 1)) : wr_ptr; | |
158 | assign n_rd_ptr = read ? ((rd_ptr == FIFO_DEPTH_MINUS_ONE) ? 0 : (rd_ptr + 1)) : rd_ptr; | |
159 | ||
160 | ||
161 | ||
162 | //********************************************* | |
163 | // The fifo counter increment on every write and | |
164 | // decrement on every read | |
165 | //**********************************************/ | |
166 | ||
167 | always @ (posedge clk) | |
168 | if (!rst_l) | |
169 | begin | |
170 | fifo_count <= 0; | |
171 | over_flow_err <= 1'b0; | |
172 | under_flow_err <= 1'b0; | |
173 | end | |
174 | else | |
175 | begin | |
176 | fifo_count <= n_fifo_count; | |
177 | over_flow_err <= n_over_flow_err; | |
178 | under_flow_err <= n_under_flow_err; | |
179 | end | |
180 | ||
181 | ||
182 | assign fifo_empty = (fifo_count == 0); | |
183 | ||
184 | assign fifo_full = (fifo_count == FIFO_DEPTH); | |
185 | ||
186 | assign fifo_almost_full = (fifo_count == FIFO_DEPTH - 1) | | |
187 | (fifo_count == FIFO_DEPTH); | |
188 | ||
189 | ||
190 | always @ (write or read or over_flow_err or under_flow_err or fifo_count) | |
191 | begin | |
192 | case ({write, read}) | |
193 | 2'b00: | |
194 | begin | |
195 | n_fifo_count = fifo_count; // No transaction | |
196 | n_over_flow_err = over_flow_err; | |
197 | n_under_flow_err = under_flow_err; | |
198 | end | |
199 | ||
200 | 2'b01: | |
201 | begin | |
202 | n_fifo_count = (fifo_count == 0) ? 0 : fifo_count - 1; | |
203 | n_over_flow_err = 1'b0; | |
204 | n_under_flow_err = (fifo_count == 0) ? 1'b1 : 1'b0; // Under flow case should not happen | |
205 | end | |
206 | ||
207 | 2'b10: | |
208 | begin | |
209 | n_fifo_count = (fifo_count == FIFO_DEPTH) ? FIFO_DEPTH : fifo_count + 1; | |
210 | n_over_flow_err = (fifo_count == FIFO_DEPTH) ? 1'b1 : 1'b0; // Over flow case shuld not happen | |
211 | n_under_flow_err = 1'b0; | |
212 | end | |
213 | ||
214 | 2'b11: | |
215 | begin | |
216 | n_fifo_count = fifo_count; // both transaction | |
217 | n_over_flow_err = 1'b0; // Over flow case shuld not happen | |
218 | n_under_flow_err = 1'b0; | |
219 | end | |
220 | ||
221 | endcase | |
222 | end | |
223 | ||
224 | endmodule |