1 --------------------------------------------------------------------------
2 --
3 -- Copyright (C) 1993, Peter J. Ashenden
4 -- Mail: Dept. Computer Science
5 -- University of Adelaide, SA 5005, Australia
6 -- e-mail: petera@cs.adelaide.edu.au
7 --
8 -- This program is free software; you can redistribute it and/or modify
9 -- it under the terms of the GNU General Public License as published by
10 -- the Free Software Foundation; either version 1, or (at your option)
11 -- any later version.
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., 675 Mass Ave, Cambridge, MA 02139, USA.
21 --
22 --------------------------------------------------------------------------
23 --
24 -- $RCSfile: ir-behaviour.vhdl,v $ $Revision: 1.1 $ $Date: 2000/05/08 14:36:48 $
25 --
26 --------------------------------------------------------------------------
27 --
28 -- Behavioural architecture of instruction register.
29 --
30
31
32 use work.dlx_instr.all;
33
34 architecture behaviour of ir is
35
36 begin
37
38 reg: process (d, latch_en, immed_sel1, immed_sel2,
39 immed_unsigned1, immed_unsigned2, immed_en1, immed_en2)
40
41 variable latched_instr : dlx_word;
42
43 use work.bv_arithmetic.bv_zext, work.bv_arithmetic.bv_sext;
44
45 begin
46 if latch_en = '1' then
47 latched_instr := d;
48 ir_out <= latched_instr after Tpd;
49 end if;
50 --
51 if immed_en1 = '1' then
52 if immed_sel1 = immed_size_16 then
53 if immed_unsigned1 = '1' then
54 immed_q1 <= bv_zext(latched_instr(16 to 31), 32) after Tpd;
55 else
56 immed_q1 <= bv_sext(latched_instr(16 to 31), 32) after Tpd;
57 end if;
58 else -- immed_sel1 = immed_size_26
59 if immed_unsigned1 = '1' then
60 immed_q1 <= bv_zext(latched_instr(6 to 31), 32) after Tpd;
61 else
62 immed_q1 <= bv_sext(latched_instr(6 to 31), 32) after Tpd;
63 end if;
64 end if;
65 else
66 immed_q1 <= null after Tpd;
67 end if;
68 --
69 if immed_en2 = '1' then
70 if immed_sel2 = immed_size_16 then
71 if immed_unsigned2 = '1' then
72 immed_q2 <= bv_zext(latched_instr(16 to 31), 32) after Tpd;
73 else
74 immed_q2 <= bv_sext(latched_instr(16 to 31), 32) after Tpd;
75 end if;
76 else -- immed_sel2 = immed_size_26
77 if immed_unsigned2 = '1' then
78 immed_q2 <= bv_zext(latched_instr(6 to 31), 32) after Tpd;
79 else
80 immed_q2 <= bv_sext(latched_instr(6 to 31), 32) after Tpd;
81 end if;
82 end if;
83 else
84 immed_q2 <= null after Tpd;
85 end if;
86 end process reg;
87
88 end behaviour;
89
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