Circuit design and transmission performance of ISDN basic interface

An LSI-based user-network interface circuit, applicable to a network terminal (NT) for the integrated services digital network (ISDN) basic interface is developed. Adaptive timing extraction, with a simplified polyphase phase-locked oscillator, is introduced into the circuit for application to both point-to-point and passive bus configurations. This circuit does not require any manual adjustment. In addition to the primitives defined by CCITT between layers one and two, a new primitive is adopted for controlling the transmission of information. This primitive avoids premature transmission due to processing delays in the exchange terminal (ET). The above functions are fabricated on a CMOS gate-array LSI chip with 4000 gates. The performance of the interface circuit is confirmed with special attention to transmission and electrical characteristics