module bin2gray4 (
input [3:0] bin_in,
output [3:0] gray_out
);
// Compact vector form (logical shift right)
assign gray_out = bin_in ^ (bin_in >> 1);
endmodule
💡Remember
- Vector trick:
bin ^ (bin >> 1) implements Binary→Gray in one line. - Bitwise vs reduction:
^ here is bitwise XOR (vector result), not reduction XOR (^bin). - Indexing matters: LSB depends on two adjacent bits (
bin[1] ^ bin[0]), MSB copies through. - Sized literals: Use
4'h* in tests to avoid width surprises. - Pure combinational: No
always needed—continuous assign is enough.
