The DS3160 device, which combines a line interface unit (LIU) with a formatter and framer, is compliant with the JT 6312kbps secondary-rate user-network interface and supports the G.704 and NTT J2 frame formats. A full-featured LIU with integrated jitter attenuator supports a software-programmable framer and formatter. Framer features include alarm and error detection, on-chip HDLC controller for processing of M-bit information, and programmable timeslot data-enable signal for 1.5Mbps, 3Mbps, 4.5Mbps, and 6Mbps frame formats. The formatter adds the required overhead to the user data and has the additional capability of generating diagnostic errors. Loopback features, together with an on-chip bit-error-rate test (BERT) function, allow easy isolation and monitoring of network segments.