The SMD103, M13 Multiplexer and De-multiplexer (M13MD), Intellectual Property (IP) block performs the functions of M13 multiplexing in the transmit direction and M13 de-multiplexing in the receive direction. The purpose of the M13 multiplexer/transmitter is to generate DS3 or E3 data channel running at 44.184 Mb/s or 34.368 Mb/s by multiplexing 28 DS1 or 21 E1 signals, respectively. Conversely, M13 de-multiplexer/receiver generates 28 DS1 or 21 E1 signals out of single DS3 signal. The Silicomotive’s M13 Multiplexer and De-multiplexer (M13MD) IP block combines the above functions and it adheres to the recommendations specified in ANSI T1.107, ITU-T G.747 and ITU-T G.751 standards.