US 6,307,891 B1 · Method and apparatus for freezing a communication link during a disruptive event

Abstract

A method and apparatus are provided for suspending or freezing outputs from an isolation barrier system, which may be a digital capacitive isolation barrier system, during the occurrence of events that may disrupt proper operation of the system. Examples of such disruptive events are data rate changes during modem baud rate negotiations, transition to low-power mode, and going off-hook in a telephony system. In each of these cases, the master circuit anticipates the disruption and sends a freeze signal to the isolated circuit. The freeze signal instructs the isolated circuit to enter freeze mode, and no data is sent through the isolation system. Internal control signals are generated and used to establish synchronization and framing after the disruption, and to restore normal operation of the isolation system. In preferred embodiments, the duration of the freeze period may be determined by a timer or by circuitry that detects framing lock or the presence of transients in the system. This invention prevents the transmission of erroneous control signals or corrupted data through the isolation system when it experiences a disruptive event.

Claims20

Dependent claims

A method for inhibiting outputs of a telephone line isolation system for the duration of a disruption in the system, the isolation system comprising a master circuit and an isolated circuit separated by an isolation barrier, the method comprising:

in the master circuit, identifying a disruptive event;
sending a freeze control signal from the master circuit to the isolated circuit across the isolation barrier to initiate a freeze mode of operation;
during freeze mode operation, inhibiting output of data and control signals from the isolated circuit to circuitry outside of the telephone line isolation system, the isolated circuit being uninhibited to transmit signals to circuitry outside of the telephone line isolation system during at least some normal operations;
restoring synchronization and framing lock in the isolated circuit after the disruptive event occurs;
and then
ending freeze mode operation and resuming normal operation of the telephone line isolation system.

3 more elements

A telephone line isolation system having a master circuit on a first side of an isolation barrier and an isolated circuit on a second side of the barrier, whereby data signals are transmitted across the isolation barrier, the telephone line isolation system comprising:

a data rate change detection circuit in the master circuit, including an output for providing a freeze signal if a data sample rate change is detected;
a transmitter circuit in the master circuit having an input connected to receive the freeze signal and an output coupled to the isolation barrier;
a receiver circuit in the isolated circuit having an input coupled to the isolation barrier;
and
a freeze control circuit in the isolated circuit, the freeze control circuit having an input connected to receive the freeze signal from the receiver circuit, the freeze control circuit being adapted to inhibit control and data outputs from the isolated circuit in response to the freeze signal,
wherein the isolated circuit is configured to transmit signals to circuitry outside of the telephone line isolation system.

3 more elements

Dependencies are inferred from the claim text.

Method and apparatus for freezing a communication link during a disruptive event

Life of this patent

Method and apparatus for freezing a communication link during a disruptive event

Life of this patent

Abstract

Claims20