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1 | // ========== Copyright Header Begin ========================================== |
2 | // | |
3 | // OpenSPARC T2 Processor File: rptr_empty.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 rptr_empty (rempty,raddr,rptr,rwptr2,rinc,rclk,rrst_n); | |
36 | parameter ADDRSIZE=6; | |
37 | ||
38 | output rempty; | |
39 | output [ADDRSIZE-1:0] raddr; | |
40 | output [ADDRSIZE:0] rptr; | |
41 | input [ADDRSIZE:0] rwptr2; | |
42 | input rinc,rclk,rrst_n; | |
43 | reg [ADDRSIZE:0] rptr,rbin,rgnext,rbnext; | |
44 | reg rempty,raddrmsb; | |
45 | ||
46 | // Gray style pointer | |
47 | ||
48 | always @(posedge rclk or negedge rrst_n) | |
49 | if ( !rrst_n) begin | |
50 | rptr <=0; | |
51 | raddrmsb <= 0; | |
52 | end | |
53 | else begin | |
54 | rptr <= rgnext; | |
55 | raddrmsb <= rgnext[ADDRSIZE]^rgnext[ADDRSIZE-1]; | |
56 | end | |
57 | ||
58 | always @(rptr or rinc or rempty ) begin: Gray_inc | |
59 | integer i; | |
60 | for (i=0; i <= ADDRSIZE; i=i+1) | |
61 | rbin[i] = ^(rptr>>i); | |
62 | if (!rempty ) rbnext = rbin + rinc; | |
63 | else rbnext = rbin; | |
64 | rgnext = (rbnext >> 1) ^ rbnext; | |
65 | end | |
66 | ||
67 | // memory read address pointer | |
68 | assign raddr = { raddrmsb,rptr[ADDRSIZE-2:0]}; | |
69 | ||
70 | // fifo empty on reset or when next rptr == synced wptr | |
71 | ||
72 | always @(posedge rclk or negedge rrst_n) | |
73 | if (!rrst_n ) rempty <= 1'b1; | |
74 | else rempty <= (rgnext == rwptr2); | |
75 | endmodule | |
76 |