American Telephone & Telegraph Co., At&t Bell Laboratories

At&t Information Systems Inc.

Cu T Than

Gregory Lese

Ralph Richardson

John D Price

Mark D Vancura

An asynchronous interface for coupling data between a terminal and a data module is provided. The asynchronous interface directly determines and matches to the rate of serial data being transmitted by the terminal and received by the data module with minimal involvement of a processor associated with the data module. The asynchronous interface determines the rate of the data being transmitted by configuring counting circuitry therein for measuring the period of the start bit in the first received character whenever the speed of data being transmitted by the terminal must be determined. The asynchronous interface then adjusts to the newly determined data rate and receives the remaining bits in the first character and subsequent characters at the new rate. The processor is involved only to request that the asynchronous interface determine the incoming data rate and match to it and, once the data rate has been determined and matched, to process the recovered characters and this new rate. While the asynchronous interface determines and matches to the incoming data rate, the processor is freed for other tasks.

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Whitehall, PA, United States of America

Cu T Than