National Semiconductor Corporation

David C Brief

James R Hamstra

Gregory Lee DeJager

James F Torgerson

Walter R Friedrich

Desmond W Young

Mark A Travaglio

A physical layer (PHY) device which can operate as a conventional PHY or as a repeater in a communication system. The PHY repeater supports four optional modes which may be enabled by programming control register bits with a microcontroller. These optional modes are: pass all symbols, enable noise filter, pass violation symbols and pass line states. When the pass all symbols, pass violation symbols and pass line states modes are enabled, the PHY device operates as a 'transparent' repeater. The repeater allows errors in a data stream to be encoded and repeated without filtering to a downstream station. The repeater also allows line states to be repeated without station management software. A single repeater may be used to couple two stations or multiple repeaters may be connected to form multi-port repeater boxes which can be connected to facilitate more reliable connections between stations.

Method and apparatus for repeating data

A physical layer (PHY) device which can operate as a conventional PHY or as an intelligent repeater in a communication system. The PHY device supports four optional modes which may be enabled by programming control register bits with a microcontroller. These optional modes are: pass all symbols, enable noise filter, pass violation symbols and pass line states. During operation as an intelligent repeater, the pass all symbols, pass violation symbols and pass line states modes are enabled. The intelligent repeater allows errors in a data stream to be encoded and repeated without filtering to a downstream station. The intelligent repeater also allows line states to be repeated without station management software. A single intelligent repeater may be used to couple two stations or multiple intelligent repeaters may be connected to form multi-port repeater boxes which can be connected to facilitate more reliable connections between stations.

Intelligent repeater functionality

An interface system for transferring information between a local area network and a system memory associated with a station attached to the network. The interface system includes a bus interface unit for implementing the transfer of information between the interface system and the memory system. An indicate module transfers information received by the interface system from the network to the memory system via the bus interface unit. A request module transfers information received by the interface system from the memory system via the bus interface unit to the network. A status generation/space management module connected to the indicate module and to the request module monitors the status thereof and generates corresponding status signals and manages the allocation of storage space in the memory system for information transferred between the network and the memory system via the interface system.

Method and apparatus for reliable descriptor chaining in a media access

Method and apparatus for receive frame sorting in a media access

Embodiments of the present invention provide methods and circuits for testing the hybrid capabilities of a station before the station is connected into an FDDI-II hybrid ring. One embodiment tests hybrid mode operation of an FDDI-II non-monitor station by creating a loopback ring, generating cycles for isochronous transmission on the loopback ring, and measuring the progress of the cycles around the loopback ring. The loopback ring created may be internal to a single integrated circuit, internal to a single slave station, or limited to a pair of stations, such as a concentrator and a single attachment station. Another embodiment provides a circuit for use in station on an FDDI-II ring. The circuit includes a loopback circuit which may be configured to create a hybrid ring and a cycle generator for generating cycles on the hybrid ring. The cycle generator includes a small latency adjustment buffer (LAB) and a limited isochronous media access control unit (IMAC) which are incapable of cycle master operation but are sufficient to provide test cycles.

Hybrid loopback for FDDI-II slave stations

In a communication network, an efficient link error monitor is provided that completely relieves the microprocessor of computing the link error rate and comparing it with link error rate thresholds. The link error rate computation and the comparison are performed by the physical layer of a communication station. The physical layer generates an interrupt to the microprocessor only if a threshold is crossed and a microprocessor action may be required. The physical layer includes a number of registers that can be conveniently written by the microprocessor to designate the thresholds and monitor the link errors. The link error rate is estimated using a simple estimator that provides a realistic link error rate estimate even at early stages of operation when few link errors have been detected and when, therefore, little statistical information on the link error rate exists.

Link error monitoring

To exchange data in the same position in the hybrid ring control cycles in two FDDI-II rings, the cycles of the different rings are phase and frequency aligned. To achieve phase alignment, a hybrid multiplexer in one of the rings monitors the cycles on the other ring and starts a cycle when the hybrid multiplexer detects a starting delimiter on the other ring. In order to achieve frequency alignment, 8 KHz references produced by two hybrid multiplexers on the two respective rings are provided to a circuit that selects one of the references to determine the frequency for synchronizing cycle outputs of both hybrid multiplexers.

Apparatus and methods for providing an interface between FDDI-II rings

A controllable physical connection management (PCM) pseudo code user interface is disclosed for use in the physical layer controller of a station or concentrator that is capable of insertion into a data transmission network that is capable of operating substantially in accordance with the FDDI protocol. In one aspect of the invention, the interface permits the user to direct the PCM state machine to pause after entering the Next state after the transmission of any pseudo code signalling bit. In another aspect of the invention, the interface permits a user to load a hardware register with the pseudo code signalling information to be transmitted before the signalling begins. However, Complete control of the pseudo code signalling is retained by the user during the signalling process to permit midstream changes in the pseudo code sequence to protect against communications with unexpected neighboring port configurations and to permit custom pseudo code signalling sequences.

PCM pseudo code signalling user interface

A controllable configuration management (CFM) state machine user interface is disclosed for use in the physical layer controller of a station or concentrator capable or insertion into a data transmission network that is capable of operating substantially in accordance with the FDDI protocol. In one aspect of the invention, the physical layer controller includes a null configuration register, a join configuration register and a loop configuration register. The null configuration register is capable of storing information indicative of a desired configuration of the physical layer controller when the CFM state machine is in a null configuration. Similarly, the join and loop configuration register are capable of storing information indicative of desired configurations when the CFM state machine is in the join and loop configurations respectively.

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Palo Alto, CA, United States of America

David C Brief