The DS21354/DS21554 single-chip transceivers (SCTs) contain all the necessary functions to connect to E1 lines. The devices are upward-compatible versions of the DS2153 and DS2154 SCTs. The on-board clock/data recovery circuitry coverts the AMI/HDB3 E1 waveforms to an NRZ serial stream. Both devices automatically adjust to E1 22AWG (0.6mm) twistedpair cables from 0 to over 2km in length. They can generate the necessary G.703 waveshapes for both 75Ω coax and 120Ω twisted cables. The on-board jitter attenuator (selectable to either 32 bits or 128 bits) can be placed in either the transmit or receive data paths. The framer locates the frame and multiframe boundaries and monitors the data stream for alarms. It is also used for extracting and inserting signaling data, Si, and Sa-bit information. The on-board HDLC controller can be used for Sa-bit links or DS0s. The devices contain a set of internal registers that the user can access to control the operation of the units. Quick access through the parallel control port allows a single controller to handle many E1 lines. The devices fully meet all the latest E1 specifications, including ITU-T G.703, G.704, G.706, G.823, G.732, and I.431, ETS 300 011, 300 233, and 300 166, as well as CTR12 and CTR4.