Patent ID: 7020187

Claim:
A method of isolating a telephone line, comprising: providing a modem circuitry; providing a system side line isolation circuitry; integrating the modem circuitry and system side line isolation circuitry within a single integrated circuit, the single integrated circuit configured to communicate through an isolation barrier; providing an asynchronous serial port on the single integrated circuit, the asynchronous serial port being configured to communicate with a system-side external circuit; configuring the single integrated circuit to use the asynchronous serial port to transfer data formatted with HDLC framing between the single integrated circuit and the system-side external circuit through the asynchronous serial port; asynchronously receiving HDLC framed data from system-side external circuit utilizing a pin on the integrated modem and system side line isolation circuitry to indicate when it is ready to receive data from the system-side external circuit; and treating as end of frame indicator a condition where no HDLC framed data is being received by the integrated modem and system side line isolation circuitry while the pin is indicating that the integrated modem and system side line isolation circuitry is ready to receive data.