Abstract: A system is disclosed that provides for the proper decoding of data information in an Encoder-Decoder ENDEC receiver in a Fiber Distributed Data Interface FDDI network. The system decouples the receiver from the data information when idle signals are provided thereto. In so doing "fragment bytes" associated with such transmission are not decoded.

Abstract: Methods and apparatus are set forth which facilitate continuous bit error rate monitoring at the physical (PHY) management layer in a Fiber Distributed Data Interface (FDDI), duel token ring network. The monitoring is performed using existing line status information from PHY. Simple error detection logic. In combination with an error counter and a timer, is used to detect errors during active or idle line state conditions, independent of Media Access Control (MAC) layer support.

Abstract: Method and apparatus suited for use with a decoder receiving data serially from a network is disclosed providing synchronization throughout reception and decoding of packets of symbols. An appropriately-delayed read pointer initialization strobe used by an elastic buffer portion of the receiver provides the sequence of synchronization signals which avoids deletion of bits of packet preamble.

Abstract: A system for adjusting the synchronizing signal received by an ENDEC receiver in a token ring network is disclosed. The system used lookahead logic in conjunction with the packet delimiter byte to adjust the synchronizing signal without delaying any bits received by the ENDEC receiver. This system has significant utility in Fiber Distributed Data Interface (FDDI) networks.

Abstract: A method and apparatus are disclosed for preserving a minimum or maximum interpacket gap length in an independently clocked data network, typically one following the ANSI-FDDI standard. A smoother is placed downstream of each elastic buffer in the network. The smoother detects the occurrence in an arriving stream of bytes of short preambles, i.e., those having fewer than a threshold number of idle bytes, and inserts some number n.sub.a additional idle bytes into such preambles. Subsequently arriving bytes are delayed by n.sub.a byte clock periods by, in a preferred embodiment, storing them in a FIFO sequence of registers. In order to be available for lengthening other short preambles when they arrive, the smoother also detects the arrival of long preambles, i.e., those having more than the threshold number of idle bytes, and deletes a number n.sub.d idle bytes from such long preambles.

Abstract: Method and apparatus is disclosed which disables which disables a repeater connected to a packet-based network so that improper symbols are not propagated. A communications management unit employing the invention would, upon reception of an improper symbol, cause transmission to halt. The invention implements a three-state machine. Reception of any improper symbol, or symbol with a parity error, causes entry into a forced-halt state. Reception of an IDLE symbol causes transition to a forced-idle state. Return to the start state occurs upon reception of a start-of-packet symbol pair.