Abstract: An encoding/decoding scheme for pulse amplitude modulation (PAM) communications systems is disclosed. In one embodiment, a transmitter unit includes an encoder circuit and a transmit circuit. The encoder circuit is configured to encode an input data word having a first number of bits into a output data word having a second number of bits. The encoder performs a comparison operation to determine if at least one pair of subsets of the second plurality of bits includes bit values that are complements of each other. The encoder is further configured to modify the second plurality of bits if none of the pairs of subsets includes a bit values that are complements of each other such that the modified second plurality of bits does include at least one pair of subsets that includes values complementary to one another.