Abstract: Packet communication employs a multiplicity of packets with interpacket gaps made up of Idle symbols between such packets. In word encoding messages for the packet prescribed alphabet symbols are employed with certain other symbols left unused. Information is advantageously added in packet communication by 1) employing unused symbols in the packet, 2) substituting in the interpacket gap symbols that are not Idle symbols but are decoded as such or, 3) using both such expedients.

Abstract: A synchronous digital decoding circuit decodes Manchester-encoded data using a clock regenerating circuit which produces a decoding clock that is continuously adjusted in accordance with detected phase deviations in the received data signal. The Manchester-encoded data are transmitted with high-to-low and low-to-high transitions at the centers of the data bit cells. On the receiving end, a digital state machine, which is coupled to a timer/counter unit, detects whether a transition is on-time, early, or late in each bit cell as compared with the established decoding clock. If the transition is early or late, the state machine produces a correction signal which is used to correspondingly shorten or lengthen the clock count by a predetermined incremental amount. The adjustment of the clock counts on an on-going basis reduces or eliminates the phase deviation and prevents the accumulation of phase error over an extended length of time. In the preferred embodiment, an oscillator input of 1.