// add4csa.e  a carry save adder, 4 bit, for a 4 bit multiplier

define add4csa(b, a[4], sum_in[4], cin[4], sum_out[4], cout[4])
  // b is a multiplier bit 
  // a is the multiplicand
  // sum_in and sum_out are what their name implies
  // cin and cout are vectors here, not single bits

signal zero[4] <= #h0;
signal aa[4];
circuits
  aa <= a when b else zero after 1ns;
  add0 use fadd(aa[0], sum_in[0], cin[0], sum_out[0], cout[0]);
  add1 use fadd(aa[1], sum_in[1], cin[1], sum_out[1], cout[1]);
  add2 use fadd(aa[2], sum_in[2], cin[2], sum_out[2], cout[2]);
  add3 use fadd(aa[3], sum_in[3], cin[3], sum_out[3], cout[3]);
end circuits;
end add4csa;