Dedicated circuitry inside the GXB transceiver channels of the gigabit transceiver block (GXB) in a Stratix^™ GX device that encodes 8-bit data into 10-bit data, or decodes 10-bit data into 8-bit data, with an equivalent number of zeros and ones, such that no more than five consecutive zeros or ones are transmitted. Complies with IEEE Std 802.3z.