VLSI concepts for integrated voice/data terminals

The driving forces behind the development of the integrated services digital network (ISDN) are increased functionality and cost benefits to the user. The many different possibilities of the ISDN can only be fully realized using new terminal equipment (from simple telephones to multiservice flexible-configuration workstations). The authors describe how recent advances in VLSI design make it possible to conceive ISDN terminals in a cost-effective way using a minimum number of optimized circuits. The proposed architecture offers a very natural and attractive upgrade path for the system designer to implement new features and voice/data services without hardware overhead to the basic terminal. The focus is on terminal implementations based on the ISDN-oriented modulator (IOM) architecture and the IOM interface. The IOM interface allows internal 64-kb/s intercommunication and includes a general asynchronous protocol for exchange of data between independent modules or microcomputer systems. Among other things, this architecture offers the user the possibility to integrate additional features as required