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
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
|
library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
use ieee.std_logic_unsigned.all;
package cru is
subtype word is std_logic_vector(31 downto 0);
constant clock_time : time := 10 ns;
type memory_type is array (0 to 1023) of std_logic_vector(31 downto 0);
end package;
library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
use ieee.std_logic_unsigned.all;
use work.cru.all;
entity reg is
port (
CLK: in std_logic; -- Rising edge -> Read; Falling edge -> Write.
W: in word; -- The data to write.
ENABLE: in std_logic; -- If 1 then at falling edge of clock, W will be written.
ZERO: in std_logic; -- If 1 then at rising edge of clock, 0 will be output to R.
R: out word -- The data to read.
);
end entity;
architecture Behavioral of reg is
signal V: word;
begin
process(CLK)
begin
if rising_edge(CLK) then
if ZERO = '1' then
R <= (others => '0');
else
R <= V;
end if;
end if;
if falling_edge(CLK) and ENABLE = '1' then
V <= W;
end if;
end process;
end architecture;
library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
use ieee.std_logic_unsigned.all;
use work.cru.all;
entity register_file is
port (
CLK: in std_logic;
ENABLE: in std_logic;
ZERO1, ZERO2: in std_logic;
R1, R2, W: in std_logic_vector(4 downto 0);
WD: in std_logic_vector(31 downto 0);
RD1, RD2: out std_logic_vector(31 downto 0)
);
end entity;
architecture Behavioral of register_file is
type reg_file_type is array (0 to 31) of std_logic_vector(31 downto 0);
signal reg_file: reg_file_type := (others => (others => '0'));
begin
process (CLK)
begin
if rising_edge(CLK) then
if ZERO1 = '1' then
RD1 <= (others => '0');
else
RD1 <= reg_file(to_integer(unsigned(R1)));
end if;
if ZERO2 = '1' then
RD2 <= (others => '0');
else
RD2 <= reg_file(to_integer(unsigned(R2)));
end if;
end if;
if falling_edge(CLK) and ENABLE = '1' then
reg_file(to_integer(unsigned(W))) <= WD;
end if;
end process;
end architecture;
library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
use ieee.std_logic_unsigned.all;
use work.cru.all;
entity alu is
port (
A, B: in std_logic_vector(31 downto 0);
ALUC: in std_logic_vector(3 downto 0);
S: out std_logic_vector(31 downto 0);
Z: out std_logic
);
end entity;
architecture Behavioral of alu is
begin
S <= A + B when ALUC(2 downto 0) ?= B"000"
else A - B when ALUC(2 downto 0) ?= B"010"
else A and B when ALUC(2 downto 0) ?= B"100"
else A or B when ALUC(2 downto 0) ?= B"101"
else A xor B when ALUC(2 downto 0) ?= B"110"
else std_logic_vector(signed(A) sll 16) and X"FFFF0000" when ALUC(2 downto 0) ?= B"110"
else std_logic_vector(signed(A) sll to_integer(unsigned(B))) when ALUC ?= B"0011"
else std_logic_vector(signed(A) srl to_integer(unsigned(B))) when ALUC ?= B"0111"
else std_logic_vector(signed(A) sra to_integer(unsigned(B))) when ALUC ?= B"1111";
Z <= S ?= X"00000000";
end architecture;
library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
use ieee.std_logic_unsigned.all;
use work.cru.all;
entity clock is
port(CLK: out std_logic);
end entity;
architecture Behavioral of clock is
begin
CLK <= not CLK after clock_time;
end architecture;
library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
use ieee.std_logic_unsigned.all;
use work.cru.all;
entity cpu is
port (memory: inout memory_type);
end entity;
architecture Behavioral of cpu is
signal pc: std_logic_vector(31 downto 0);
signal pc_to_write: std_logic_vector(31 downto 0);
signal enable_mem: std_logic;
signal write_mem: std_logic;
signal CLK: std_logic;
signal WRITE_REG: std_logic;
signal ZERO1, ZERO2: std_logic;
signal R1, R2, W: std_logic_vector(4 downto 0);
signal WD: std_logic_vector(31 downto 0);
signal RD1, RD2: std_logic_vector(31 downto 0);
signal A, B: std_logic_vector(31 downto 0);
signal ALUC: std_logic_vector(3 downto 0);
signal S: std_logic_vector(31 downto 0);
signal Z: std_logic;
begin
pc_reg: entity work.reg
port map (
CLK => CLK,
ENABLE => '1',
ZERO => '0',
W => pc_to_write,
R => pc
);
reg: entity work.register_file
port map(
CLK => CLK,
ENABLE => WRITE_REG,
ZERO1 => ZERO1,
ZERO2 => ZERO2,
R1 => R1,
R2 => R2,
W => W,
WD => WD,
RD1 => RD1,
RD2 => RD2
);
alu: entity work.alu
port map(
A => A,
B => B,
ALUC => ALUC,
S => S,
Z => Z
);
logic: process is
variable ins: std_logic_vector(31 downto 0);
begin
ins := memory(to_integer(unsigned(pc)));
pc_to_write <= pc + B"1";
WRITE_REG <= '0';
enable_mem <= '0';
if ins(31 downto 16) = B"000010" then
pc_to_write(25 downto 0) <= ins(25 downto 0);
pc_to_write(31 downto 26) <= (others => '0');
elsif ins(31 downto 16) = B"000011" then
W <= B"00001";
WD <= pc_to_write;
WRITE_REG <= '1';
pc_to_write(25 downto 0) <= ins(25 downto 0);
pc_to_write(31 downto 26) <= (others => '0');
elsif ins(31 downto 26) = B"000000" then
if ins(5) = '1' then
R1 <= ins(25 downto 21);
R2 <= ins(20 downto 16);
ALUC <= ins(3 downto 0);
A <= RD1;
B <= RD2;
W <= ins(15 downto 11);
WRITE_REG <= '1';
WD <= S;
elsif ins(3) = '0' then
R1 <= ins(20 downto 16);
ALUC(3 downto 2) <= ins(1 downto 0);
ALUC(1 downto 0) <= B"11";
A <= RD1;
B(31 downto 5) <= (others => '0');
B(4 downto 0) <= ins(10 downto 6);
W <= ins(15 downto 11);
WRITE_REG <= '1';
WD <= S;
else
R1 <= ins(25 downto 21);
WRITE_REG <= '0';
pc_to_write <= RD1;
end if;
else
if ins(31) = '1' then
enable_mem <= '1';
R1 <= ins(25 downto 21);
ALUC <= B"0000";
A <= RD1;
B(15 downto 0) <= ins(15 downto 0);
B(31 downto 16) <= X"0000";
if ins(29) = '1' then
W <= ins(20 downto 16);
write_mem <= '0';
else
R2 <= ins(20 downto 16);
write_mem <= '1';
end if;
elsif ins(29 downto 26) = B"1111" then
WRITE_REG <= '1';
W <= ins(20 downto 16);
WD(31 downto 16) <= ins(15 downto 0);
elsif ins(29) = '1' then
R1 <= ins(25 downto 21);
ALUC <= ins(29 downto 26);
A <= RD1;
B(15 downto 0) <= ins(15 downto 0);
B(31 downto 16) <= X"0000";
W <= ins(20 downto 16);
WRITE_REG <= '1';
WD <= S;
else
R1 <= ins(25 downto 21);
R2 <= ins(20 downto 16);
ALUC <= B"0010";
A <= RD1;
B <= RD2;
if Z = '1' then
pc_to_write <= pc_to_write + ins(15 downto 0);
end if;
WRITE_REG <= '0';
end if;
end if;
if enable_mem then
if write_mem then
WRITE_REG <= '0';
memory(to_integer(unsigned(S))) <= RD2;
else
WRITE_REG <= '1';
WD <= memory(to_integer(unsigned(S)));
end if;
end if;
wait for 1ns;
end process;
end architecture;
|
