Abstract: A modem (20) receiving high speed digital data from data terminal equipment (10). The modem operates in a "software UART" state when in command mode. A high speed clock (30) is used to continually take samples of an incoming signal from a DTE (10). A microprocessor (40) multitasks between analyzing the samples taken from the incoming signal and generating output signals to be sent to the DTE (10). The high speed clock is adjustable, setting the sample rate to be a integer multiple of at least eight times all the possible bit rates of the incoming signal. This permits quicker autobauding. Commands and prefixes can be received and detected simultaneously with the transmission of result codes to previous commands.

Abstract: Method and apparatus for reducing latency delay associated with converting asynchronous, serial digital data to packet data. The number of data characters received before a time-out occurs are counted; the last character received before a time-out occurs is recognized; or the number of data characters transmitted before a signal is received from the destination terminal are counted. The information thus gathered is used to predict the occurrence of future latency delay. Data packets are transmitted immediately upon the subsequent receipt of a number of data characters equal to the number of data characters received before the time-out occurred; receipt of a character identical to the last character received before a time-out; or receipt of a number of data characters equal to the number of data characters transmitted before another signal is received from the destination terminal, respectively. By transmitting immediately when a latency delay is expected, the latency delay is completely avoided.

Abstract: A method for communicating with a plurality of hosts connected to an X.25 network and for selectably using a character as a control character or a data character. Each character received from the X.25 network is inspected to determine if it is one of a set of reserved characters. If so, the character is encoded before being sent to its final destination. Data intended for the X.25 network is inspected for the presence of a predetermined control character. If the control character is present, the next character is inspected to determine whether it is a command character or an encoded data character. If this next character is an encoded data character, it is decoded and provided to the X.25 network. If this next character is a command character, then the command is executed. The method allows the use of any character as either a command character or data character. Data transfer between the DTE and DCE is assigned a PAD and a virtual channel number which corresponds to a particular host on the X.25 network.

Abstract: A modem with improved signal processing and handshaking capabilities as described. Two digital signal processors are used to perform independent, concurrent operations so that a faster execution rate is obtained and more precise calculations are made possible. The modem also uses an improved handshaking technique which allows the modem to maintain compatibility with existing 1200 and 2400 bps modems while allowing for negotiation for 4800 and 9600 bps communications. The modem also incorporates an improved baud clock recovery circuit which dynamically adjusts the actual sampling point in a manner dependent upon the difference between the actual sampling point and the optimal sampling point. This allows the actual sampling point to converge upon the desired sampling point at a high rate while minimizing jitter around the optimal sampling point.