diff --git a/stdlib/rtl/oh_lfsr.v b/stdlib/rtl/oh_lfsr.v new file mode 100644 index 0000000..e7066fb --- /dev/null +++ b/stdlib/rtl/oh_lfsr.v @@ -0,0 +1,58 @@ +//############################################################################# +//# Function: Random number generator # +//############################################################################# +//# Author: Andreas Olofsson # +//# License: MIT (see LICENSE file in OH! repository) # +//############################################################################# +// +// References: +// https://users.ece.cmu.edu/~koopman/lfsr/index.html +// +//############################################################################ +module oh_random + #(parameter N = 32 //support multiple of 32 for now... + ) + ( + input clk, + input nreset, //async reset + input en, // enable counter + input [1:0] mode,// 0=fibonacci,1=galois + input lsbfirst,// 1=shift from lsb, 0=shift from msb + input [N-1:0] taps, // taps + input [N-1:0] seed, // seed + input [N-1:0] mask, // mask output (1 = active) + output [N-1:0] out // output value + ); + + // TODO: support non-multiples of 32 + reg [N-1:0] lfsr_reg[0:N/32-1]; + wire [N-1:0] lfsr_in[0:N/32-1]; + wire [N-1:0] taps_sel[0:N/32-1]; + wire [N/32-1:0] feedback; + + // instantiate multiple 32bit rngs + genvar i,j; + generate + for(i=0;i<(N/32);i=i+1) begin + //taps + assign taps_sel[i] = entaps ? taps[(i+1)*32-1:i*32]: 32'h80000057 << 1; + //lfsr reg + always @(posedge clk or negedge nreset) + if(~nreset) + lfsr_reg[i] <= seed[(i+1)*32-1:i*32]; + else if(en) + lfsr_reg[i] <= lfsr_in[i]; + // feeback + assign feedback[i] = lfsr_reg[i][31]; + assign lfsr_in[i][0] = feedback[i]; + for(j=1;j<32;j=j+1) begin + assign lfsr_in[i][j] = taps_sel[i][j] ? (lfsr_reg[i][j-1] ^ feedback[i]) : + lfsr_reg[i][j-1]; + + end + assign out[(i+1)*32-1:i*32] = mask[(i+1)*32-1:i*32] & lfsr_reg[i]; + end // for (i=0;