hdlbits-Vector5

Vector5

Given five 1-bit signals (a, b, c, d, and e), compute all 25 pairwise one-bit comparisons in the 25-bit output vector. The output should be 1 if the two bits being compared are equal.

out[24] = ~a ^ a;   // a == a, so out[24] is always 1.
out[23] = ~a ^ b;
out[22] = ~a ^ c;
...
out[ 1] = ~e ^ d;
out[ 0] = ~e ^ e;

Vector5

As the diagram shows, this can be done more easily using the replication and concatenation operators.

• The top vector is a concatenation of 5 repeats of each input
• The bottom vector is 5 repeats of a concatenation of the 5 inputs

solution

module top_module (
    input a, b, c, d, e,
    output [24:0] out );//

    // The output is XNOR of two vectors created by 
    // concatenating and replicating the five inputs.
    // assign out = ~{ ... } ^ { ... };
    assign out = ~{ {5{a}}, {5{b}}, {5{c}}, {5{d}}, {5{e}} } ^ { {5{a,b,c,d,e}} };
endmodule