Content-addressable memory (CAM) is a special typeof computer memory used in certain very high speed searching applications. It is also known as associative memory, associative storage, or associative array, although the last term is more often used for a programming data structure. (Hannum et al., 2004) Several custom computers, like the Goodyear STARAN, were built to implement CAM, and were referred to as associative computers.
1 //-----------------------------------------------------
2 // Design Name : cam
3 // File Name : cam.v
4 // Function : CAM
5 // Coder : Deepak Kumar Tala
6 //-----------------------------------------------------
7 module cam (
8 clk , // Cam clock
9 cam_enable , // Cam enable
10 cam_data_in , // Cam data to match
11 cam_hit_out , // Cam match has happened
12 cam_addr_out // Cam output address
13 );
14
15 parameter ADDR_WIDTH = 8;
16 parameter DEPTH = 1 << ADDR_WIDTH;
17 //------------Input Ports--------------
18 input clk;
19 input cam_enable;
20 input [DEPTH-1:0] cam_data_in;
21 //----------Output Ports--------------
22 output cam_hit_out;
23 output [ADDR_WIDTH-1:0] cam_addr_out;
24 //------------Internal Variables--------
25 reg [ADDR_WIDTH-1:0] cam_addr_out;
26 reg cam_hit_out;
27 reg [ADDR_WIDTH-1:0] cam_addr_combo;
28 reg cam_hit_combo;
29 reg found_match;
30 integer i;
31 //-------------Code Starts Here-------
32 always @(cam_data_in) begin
33 cam_addr_combo = {ADDR_WIDTH{1'b0}};
34 found_match = 1'b0;
35 cam_hit_combo = 1'b0;
36 for (i=0; ibegin
37 if (cam_data_in[i] && ! found_match) begin
38 found_match = 1'b1;
39 cam_hit_combo = 1'b1;
40 cam_addr_combo = i;
41 end else begin
42 found_match = found_match;
43 cam_hit_combo = cam_hit_combo;
44 cam_addr_combo = cam_addr_combo;
45 end
46 end
47 end
48
49 // Register the outputs
50 always @(posedge clk) begin
51 if (cam_enable) begin
52 cam_hit_out <= cam_hit_combo;
53 cam_addr_out <= cam_addr_combo;
54 end else begin
55 cam_hit_out <= 1'b0;
56 cam_addr_out <= {ADDR_WIDTH{1'b0}};
57 end
58 end
59
60 endmodule
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