Introduction
The PEB 2085/2086 ISAC®-S implements the four-wire S/T interface used to link voice/data terminals to an ISDN.
The PEB 2085 combines the functions of the S-Bus Interface Circuit (SBC: PEB 2080) and the ISDN Communications Controller (ICC: PEB 2070) on one chip.

The component switches B and D channels between the S/T and the ISDN Oriented Modular (IOM®) interfaces, the latter being a standard backplane interface for the ISDN basic access.

The device provides all electrical and logical functions of the S/T interface, such as: activation/deactivation, mode dependent timing recovery and D channel access and priority control. The HDLC packets of the ISDN D channel are handled by the ISAC-S which interfaces them to the associated microcontroller. In one of its operating modes the device offers high level support of layer-2 functions of the LAPD protocol.

The ISAC-S is a CMOS device, available in a P-DIP-40 (PEB 2085 only), P-LCC-44 and P-MQFP-64 (PEB 2086 only) package. It operates from a single + 5 V supply and features a power-down state with very low power consumption.