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270 lines (240 loc) · 10.7 KB
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////////////////////////////////////////////////////////////////////////////////
// Company: 奥新智能
// Engineer: 耿慧慧
//
// Description: A fast base-2 logarithm function
//
// Revision: N/A
// Additional Comments:
//
////////////////////////////////////////////////////////////////////////////////
module math_log2 #(
parameter DIN_WIDTH = 64,
parameter DIN_DECI_WIDTH = 0,
parameter DOUT_WIDTH = 10,
parameter DOUT_DECI_WIDTH = 4,
// derived parameters
localparam DIN_INT_WIDTH = DIN_WIDTH-DIN_DECI_WIDTH,
localparam DOUT_INT_WIDTH = DOUT_WIDTH-DOUT_DECI_WIDTH,
// bit width parameters
localparam W1 = DIN_WIDTH-1,
localparam W2 = DOUT_WIDTH-1,
localparam W3 = DOUT_INT_WIDTH-1,
localparam W4 = DOUT_DECI_WIDTH-1,
localparam W5 = DIN_INT_WIDTH-1,
localparam W6 = W1-4
) (
input [W1:0] DIN,
input clk,
output [W2:0] DOUT
);
// Comprises 3 main blocks: priority encoder, barrel shifter, and LUT
reg [W3:0] priencout1;
(*dont_touch="true"*)reg [W4:0] LUTout;
reg [W3:0] priencout2;
(*dont_touch="true"*)reg [W3:0] priencout3;
reg [W6:0] barrelin ;
reg [ 4:0] barrelout ;
assign DOUT = {priencout3, LUTout}; // Basic top-level connectivity
// Barrel shifter - OMG, it's a primitive in Verilog!
wire [W5:0] priencin = DIN[W1:DIN_DECI_WIDTH];
wire [W6:0] tmp1 = (barrelin << ~priencout1);
always @(posedge clk) begin
barrelout <= tmp1[W1-4:W1-8];
end
// Priority encoder
always @(posedge clk) begin
priencout2 <= priencout1;
priencout3 <= priencout2;
barrelin <= DIN[W1-1:3];
end
always @(posedge clk)
casex (priencin)
64'b1xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 63;
64'b01xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 62;
64'b001xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 61;
64'b0001xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 60;
64'b00001xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 59;
64'b000001xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 58;
64'b0000001xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 57;
64'b00000001xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 56;
64'b000000001xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 55;
64'b0000000001xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 54;
64'b00000000001xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 53;
64'b000000000001xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 52;
64'b0000000000001xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 51;
64'b00000000000001xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 50;
64'b000000000000001xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 49;
64'b0000000000000001xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 48;
64'b00000000000000001xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 47;
64'b000000000000000001xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 46;
64'b0000000000000000001xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 45;
64'b00000000000000000001xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 44;
64'b000000000000000000001xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 43;
64'b0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 42;
64'b00000000000000000000001xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 41;
64'b000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 40;
64'b0000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 39;
64'b00000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 38;
64'b000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 37;
64'b0000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 36;
64'b00000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 35;
64'b000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 34;
64'b0000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 33;
64'b00000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 32;
64'b000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 31;
64'b0000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 30;
64'b00000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 29;
64'b000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 28;
64'b0000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 27;
64'b00000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 26;
64'b000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 25;
64'b0000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 24;
64'b00000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 23;
64'b000000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxx: priencout1 <= 22;
64'b0000000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxx: priencout1 <= 21;
64'b00000000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxx: priencout1 <= 20;
64'b000000000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxx: priencout1 <= 19;
64'b0000000000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxx: priencout1 <= 18;
64'b00000000000000000000000000000000000000000000001xxxxxxxxxxxxxxxxx: priencout1 <= 17;
64'b000000000000000000000000000000000000000000000001xxxxxxxxxxxxxxxx: priencout1 <= 16;
64'b0000000000000000000000000000000000000000000000001xxxxxxxxxxxxxxx: priencout1 <= 15;
64'b00000000000000000000000000000000000000000000000001xxxxxxxxxxxxxx: priencout1 <= 14;
64'b000000000000000000000000000000000000000000000000001xxxxxxxxxxxxx: priencout1 <= 13;
64'b0000000000000000000000000000000000000000000000000001xxxxxxxxxxxx: priencout1 <= 12;
64'b00000000000000000000000000000000000000000000000000001xxxxxxxxxxx: priencout1 <= 11;
64'b000000000000000000000000000000000000000000000000000001xxxxxxxxxx: priencout1 <= 10;
64'b0000000000000000000000000000000000000000000000000000001xxxxxxxxx: priencout1 <= 9;
64'b00000000000000000000000000000000000000000000000000000001xxxxxxxx: priencout1 <= 8;
64'b000000000000000000000000000000000000000000000000000000001xxxxxxx: priencout1 <= 7;
64'b0000000000000000000000000000000000000000000000000000000001xxxxxx: priencout1 <= 6;
64'b00000000000000000000000000000000000000000000000000000000001xxxxx: priencout1 <= 5;
64'b000000000000000000000000000000000000000000000000000000000001xxxx: priencout1 <= 4;
64'b0000000000000000000000000000000000000000000000000000000000001xxx: priencout1 <= 3;
64'b00000000000000000000000000000000000000000000000000000000000001xx: priencout1 <= 2;
64'b000000000000000000000000000000000000000000000000000000000000001x: priencout1 <= 1;
64'b000000000000000000000000000000000000000000000000000000000000000x: priencout1 <= 0;
endcase
/*
LUT for log fraction lookup
- can be done with array or case:
case (addr)
0:out=0;
.
31:out=15;
endcase
OR
wire [3:0] lut [0:31];
assign lut[0] = 0;
.
assign lut[31] = 15;
Are there any better ways?
*/
// Let's try "case".
// The equation is: output = log2(1+input/32)*16
// For larger tables, better to generate a separate data file using a program!
/* always @*
case (barrelout)
0 : LUTout = 0;
1 : LUTout = 0;
2 : LUTout = 1;
3 : LUTout = 2;
4 : LUTout = 2;
5 : LUTout = 3;
6 : LUTout = 4;
7 : LUTout = 4;
8 : LUTout = 5;
9 : LUTout = 6;
10: LUTout = 6;
11: LUTout = 7;
12: LUTout = 7;
13: LUTout = 8;
14: LUTout = 9;
15: LUTout = 9;
16: LUTout = 10;
17: LUTout = 10;
18: LUTout = 11;
19: LUTout = 12;
20: LUTout = 12;
21: LUTout = 13;
22: LUTout = 13;
23: LUTout = 14;
24: LUTout = 14;
25: LUTout = 15;
26: LUTout = 15;
27: LUTout = 16;
28: LUTout = 16; // calculated value is *slightly* closer to 15, but 14 makes for a smoother curve!
29: LUTout = 17;
30: LUTout = 17;
31: LUTout = 18;
32: LUTout = 18;
33: LUTout = 19;
34: LUTout = 19;
35: LUTout = 20;
36: LUTout = 20;
37: LUTout = 21;
38: LUTout = 21;
39: LUTout = 21;
40: LUTout = 22;
41: LUTout = 22;
42: LUTout = 23;
43: LUTout = 23;
44: LUTout = 24;
45: LUTout = 24;
46: LUTout = 25;
47: LUTout = 25;
48: LUTout = 25;
49: LUTout = 26;
50: LUTout = 26;
51: LUTout = 27;
52: LUTout = 27;
53: LUTout = 27;
54: LUTout = 28;
55: LUTout = 28;
56: LUTout = 29;
57: LUTout = 29;
58: LUTout = 29;
59: LUTout = 30;
60: LUTout = 30; // calculated value is *slightly* closer to 15, but 14 makes for a smoother curve!
61: LUTout = 30;
62: LUTout = 31;
63: LUTout = 31;
endcase */
always @(posedge clk)
case (barrelout)
0 : LUTout <= 0;
1 : LUTout <= 1;
2 : LUTout <= 1;
3 : LUTout <= 2;
4 : LUTout <= 3;
5 : LUTout <= 3;
6 : LUTout <= 4;
7 : LUTout <= 5;
8 : LUTout <= 5;
9 : LUTout <= 6;
10: LUTout <= 6;
11: LUTout <= 7;
12: LUTout <= 7;
13: LUTout <= 8;
14: LUTout <= 8;
15: LUTout <= 9;
16: LUTout <= 9;
17: LUTout <= 10;
18: LUTout <= 10;
19: LUTout <= 11;
20: LUTout <= 11;
21: LUTout <= 12;
22: LUTout <= 12;
23: LUTout <= 13;
24: LUTout <= 13;
25: LUTout <= 13;
26: LUTout <= 14;
27: LUTout <= 14;
28: LUTout <= 14;
29: LUTout <= 15;
30: LUTout <= 15;
31: LUTout <= 15;
endcase
endmodule
////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////