/
fmlarb_dack.v
82 lines (71 loc) · 1.71 KB
/
fmlarb_dack.v
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
/*
* Milkymist SoC
* Copyright (C) 2007, 2008, 2009, 2010, 2011 Sebastien Bourdeauducq
*
* This program 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, version 3 of the License.
*
* This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
*/
/*
* Generate ack signal from early ack signal and mask strobe.
* After an early acked write, it should pulse after 2 cycles.
* After an early acked read, it should pulse after CL+3 cycles, that is
* 5 cycles when tim_cas = 0 (assumed here)
* 6 cycles when tim_cas = 1
*/
module fmlarb_dack(
input sys_clk,
input sys_rst,
input stb,
input eack,
input we,
output stbm,
output reg ack
);
wire read = eack & ~we;
wire write = eack & we;
reg ack_read2;
reg ack_read1;
reg ack_read0;
always @(posedge sys_clk) begin
if(sys_rst) begin
ack_read2 <= 1'b0;
ack_read1 <= 1'b0;
ack_read0 <= 1'b0;
end else begin
ack_read2 <= read;
ack_read1 <= ack_read2;
ack_read0 <= ack_read1;
end
end
reg ack0;
always @(posedge sys_clk) begin
if(sys_rst) begin
ack0 <= 1'b0;
ack <= 1'b0;
end else begin
ack0 <= ack_read0|write;
ack <= ack0;
end
end
reg mask;
assign stbm = stb & ~mask;
always @(posedge sys_clk) begin
if(sys_rst)
mask <= 1'b0;
else begin
if(eack)
mask <= 1'b1;
if(ack)
mask <= 1'b0;
end
end
endmodule