This white paper gives an overview of ISDN modem technologies and how Xilinx high volume programmable devices can be used to implement complex system level glue in ISDN modem designs. The Xilinx device families targeted at these high volume applications include XC9500 CPLDs and Spartan FPGAs.

The flow of this document will be start with an overview of ISDN technology and how ISDN modems are used. We will next examine the major functional blocks of an ISDN modem and give an overview of the Application Specific Standard Products (ASSPs) that implement ISDN functions. We will then illustrate the system level glue functions that are needed by way of a design example.