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
|
-- Copyright (C) 1996 Morgan Kaufmann Publishers, Inc
-- This file is part of VESTs (Vhdl tESTs).
-- VESTs 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.
-- VESTs 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 VESTs; if not, write to the Free Software Foundation,
-- Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
-- ---------------------------------------------------------------------
--
-- $Id: ch_21_fg_21_05.vhd,v 1.2 2001-10-26 16:29:37 paw Exp $
-- $Revision: 1.2 $
--
-- ---------------------------------------------------------------------
entity SR_flipflop is
port ( s_n, r_n : in bit; q, q_n : inout bit );
begin
postponed process (q, q_n) is
begin
assert now = 0 fs or q = not q_n
report "implementation error: q /= not q_n";
end postponed process;
end entity SR_flipflop;
--------------------------------------------------
architecture dataflow of SR_flipflop is
begin
gate_1 : q <= s_n nand q_n;
gate_2 : q_n <= r_n nand q;
end architecture dataflow;
-- not in book
entity fg_21_05 is
end entity fg_21_05;
architecture test of fg_21_05 is
signal s_n, r_n, q, q_n : bit;
begin
dut : entity work.SR_flipflop
port map ( s_n, r_n, q, q_n );
s_n <= '1',
'0' after 10 ns, '1' after 15 ns,
'0' after 30 ns, '1' after 40 ns;
r_n <= '0', '1' after 5 ns,
'0' after 20 ns, '1' after 25 ns,
'0' after 30 ns, '1' after 35 ns;
end architecture test;
-- end not in book
|
