The DS2156 is a software-selectable T1, E1, or J1 single-chip transceiver (SCT) for short-haul and long-haul applications. The backplane is userconfigurable for a TDM or UTOPIA II bus interface. The DS2156 is composed of a line interface unit (LIU), framer, HDLC controllers, and a UTOPIA/TDM backplane interface, and is controlled by an 8-bit parallel port configured for Intel or Motorola bus operations. The DS2156 is pin and software compatible with the DS2155. The LIU is composed of transmit and receive interfaces and a jitter attenuator. The transmit interface is responsible for generating the necessary waveshapes for driving the network and providing the correct source impedance depending on the type of media used. T1 waveform generation includes DSX-1 line buildouts as well as CSU line buildouts of -7.5dB, -15dB, and -22.5dB. E1 waveform generation includes G.703 waveshapes for both 75 coax and 120 twisted cables. The receive interface provides network termination and recovers clock and data from the network.