Fix syntax errors and make it compile in verilator.
[firearm.git] / icache.v
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1/* 16 cache entries, 64-byte long cache lines */
2
3module ICache(
4 input clk,
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5
6 /* ARM core interface */
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7 input [31:0] rd_addr,
8 input rd_req,
9 output reg rd_wait,
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10 output reg [31:0] rd_data,
11
12 /* bus interface */
13 output reg bus_req,
14 input bus_ack,
15 output reg [31:0] bus_addr,
28c904cc 16 input [31:0] bus_data,
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17 output reg bus_rd,
18 output wire bus_wr,
19 input bus_ready);
20
21 assign bus_wr = 0;
7e757d70 22
f83818d5 23 /* [31 tag 10] [9 cache index 6] [5 data index 0]
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24 * so the data index is 6 bits long
25 * so the cache index is 4 bits long
f83818d5 26 * so the tag is 22 bits long. c.c
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27 */
28
29 reg cache_valid [15:0];
f83818d5 30 reg [21:0] cache_tags [15:0];
28c904cc 31 reg [31:0] cache_data [15:0 /* line */] [15:0 /* word */];
7e757d70 32
28c904cc 33 reg [3:0] i;
7e757d70 34 initial
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35 for (i = 0; i <= 15; i = i + 1)
36 cache_valid[i] = 0;
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37
38 wire [5:0] rd_didx = rd_addr[5:0];
39 wire [3:0] rd_didx_word = rd_didx[5:2];
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40 wire [3:0] rd_idx = rd_addr[9:6];
41 wire [21:0] rd_tag = rd_addr[31:10];
7e757d70 42
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43 wire cache_hit = cache_valid[rd_idx] && (cache_tags[rd_idx] == rd_tag);
44
7e757d70 45 always @(*) begin /* XXX does this work nowadays? */
327f45ff 46 rd_wait = rd_req && !cache_hit;
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47 rd_data = cache_data[rd_idx][rd_didx_word];
48 end
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49
50 reg [3:0] cache_fill_pos = 0;
28c904cc 51 always @(*)
327f45ff 52 if (rd_req && !cache_hit) begin
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53 bus_req = 1;
54 if (bus_ack) begin
55 bus_addr = {rd_addr[31:6], cache_fill_pos[3:0], 2'b00 /* reads are 32-bits */};
56 bus_rd = 1;
57 end
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58 end else begin
59 bus_req = 0;
60 bus_addr = 0;
61 bus_rd = 0;
62 end
63
64 always @(posedge clk)
65 if (rd_req && !cache_hit) begin
66 if (bus_ready) begin /* Started the fill, and we have data. */
67 cache_data[rd_idx][cache_fill_pos] = bus_data;
68 cache_fill_pos <= cache_fill_pos + 1;
69 if ((cache_fill_pos + 1) == 0) begin /* Done? */
70 cache_tags[rd_idx] = rd_tag;
71 cache_valid[rd_idx] = 1;
72 end
73 end
c808669d 74 end
7e757d70 75endmodule
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