Automatic synchronous/asynchronous modem
First Claim
1. A circuit for interposition between a communication line and a processor, said communication line having data transmission thereon, said circuit comprisingmeans for monitoring each new data transmission on said communication line for a preset interval at the start of said new data transmission,means operable under control of said monitoring means for detecting whether a particular new data transmission is in synchronous format or in asynchronous format, andmeans for providing a first signal when a new one of said data transmissions is detected as being synchronous and for providing a different signal when said new data transmission is detected as being asynchronous.
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Accused Products
Abstract
There is disclosed an arrangement which enables a single modem port to be used for either synchronous or asynchronous data transmission, with no manual changes required. The modem determines whether the incoming call is synchronous or asynchronous by detecting the presence (or absence) of SYNC characters in the data stream immediately after handshaking. Once a determination has been made, the modem options itself accordingly for synchronous or asynchronous data handling. This arrangement eliminates the need for separate central office lines for synchronous and asynchronous data applications.
22 Citations
12 Claims
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1. A circuit for interposition between a communication line and a processor, said communication line having data transmission thereon, said circuit comprising
means for monitoring each new data transmission on said communication line for a preset interval at the start of said new data transmission, means operable under control of said monitoring means for detecting whether a particular new data transmission is in synchronous format or in asynchronous format, and means for providing a first signal when a new one of said data transmissions is detected as being synchronous and for providing a different signal when said new data transmission is detected as being asynchronous.
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8. A signal processing device for use between data transmitting and data receiving devices, said signal processing device operable for controlling data transmissions between said data devices in either of two transmission modes, said modes characterized by data patterns within said transmission unique to said transmission mode, said signal processing device comprising
means for establishing a preset interval, means for establishing a series of data bytes each said byte having n data bits, means for examining any said established bytes, means for comparing successive ones of said examined data bytes to determine if a certain preset number m of said compared data bytes are the same, and means for providing a first signal indicative of one of said transmission modes to a receiving data transmission device upon a determination that said preset number m of consecutive data bytes is the same within said preset interval.
Specification