acs1_0.v

viterbi译码器的一种fpga实现

//Actually the node is a CSA and not an ACS.
`include "defs.h"

module ACS1_0(metric0,  metric1,  
			sum_enc_bits,   
			new_metric0,  new_metric1,  compare);

input   [8-1:0] metric0,  metric1;
input   [4-1:0] sum_enc_bits;
output  [8-1:0] new_metric0,  new_metric1;
output  compare;


wire   [`W-1:0] sub_metrs = ~metric0 + metric1;
wire   compare = sub_metrs[`W-1];

wire   [`W-1:0] survival = (compare == 1 ? metric0 : metric1);


wire   [`S-1:0] metric_change = sum_enc_bits;  // metric change
wire   [`W-1:0] signext_m = {{`W-`S{metric_change[`S-1]}}, 
 metric_change};
assign new_metric0 = survival + signext_m;
assign new_metric1 = survival - signext_m;

endmodule