Abstract: The present invention relates to a coding apparatus for encoding data represented by 8 bit input symbols into 12 bit output codes for serially transmitting the codes along a communication channel, the codes being represented in the channel by signals having a limited minimum and maximum pulse width and sampled by a receiver at each receiver's clock period. The invention reduces artifacts introduced by sending data at a higher payload rate than the bandwidth of the communication channel, such as the voltage and current offsets introduced in the data at the receiver as a function of the preceding data.