In one embodiment, a configurable communications system accommodates a plurality of different transmission word sizes. In a transmit path, the system inserts a number of padding bits corresponding to missing user-data bits onto the end of an input data sequence to generate a set of data having N bits. The N bits are interleaved and error-correction (EC) encoded to generate parity bits corresponding to an EC codeword. The parity bits are de-interleaved and multiplexed with the input data stream to generate a transmission word. In a receive path, a channel detector recovers channel values corresponding to the transmission word. Padding values, corresponding to the missing-bit locations, are inserted among the channel values. The resulting channel values are interleaved and EC decoded to recover the EC codeword. The data bits of the codeword are de-interleaved, and the padding bits corresponding to the missing channel values are discarded.