Apparatus including a shared device in communication with a plurality of computing machines external to the shared device, the shared device including at least one PTP domain coefficient storage area, the at least one PTP domain coefficient storage area receiving a PTP coefficient from a computing machine having a PTP client, and providing the PTP coefficient to a computing machine not having a PTP client. Related apparatus and methods are also provided.

A method and system that provides for execution of a first calibration sequence, such as upon initialization of a system, to establish an operation value, which utilizes an algorithm intended to be exhaustive, and executing a second calibration sequence from time to time, to measure drift in the parameter, and to update the operation value in response to the measured drift. The second calibration sequence utilizes less resources of the communication channel than does the first calibration sequence. In one embodiment, the first calibration sequence for measurement and convergence on the operation value utilizes long calibration patterns, such as codes that are greater than 30 bytes, or pseudorandom bit sequences having lengths of 2.sup.N−1 bits, where N is equal to or greater than 7, while the second calibration sequence utilizes short calibration patterns, such as fixed codes less than 16 bytes, and for example as short as 2 bytes long.

A method and system that provides for execution of a first calibration sequence, such as upon initialization of a system, to establish an operation value, which utilizes an algorithm intended to be exhaustive, and executing a second calibration sequence from time to time, to measure drift in the parameter, and to update the operation value in response to the measured drift. The second calibration sequence utilizes less resources of the communication channel than does the first calibration sequence. In one embodiment, the first calibration sequence for measurement and convergence on the operation value utilizes long calibration patterns, such as codes that are greater than 30 bytes, or pseudorandom bit sequences having lengths of 2.sup.N−1 bits, where N is equal to or greater than 7, while the second calibration sequence utilizes short calibration patterns, such as fixed codes less than 16 bytes, and for example as short as 2 bytes long.

An item of ONU equipment configures itself for communicating via a first transport system with an item of OLT equipment in an optical access network, and starts a synchronisation for the first transport system and transmits via the first transport system. The OLT equipment transmits, via a protocol layer fitting on top of the entire transport system of the optical access network, without waiting for the synchronisation for the first transport system to have ended, a message indicating which transport system is to be used by the ONU equipment. When the transport system to be used by the ONU equipment is the first transport system, the synchronisation continues the first communication system, otherwise the synchronisation is restarted for the second transport system.

An item of ONU equipment configures itself for communicating via a first transport system with an item of OLT equipment in an optical access network, and starts a synchronisation for the first transport system and transmits via the first transport system. The OLT equipment transmits, via a protocol layer fitting on top of the entire transport system of the optical access network, without waiting for the synchronisation for the first transport system to have ended, a message indicating which transport system is to be used by the ONU equipment. When the transport system to be used by the ONU equipment is the first transport system, the synchronisation continues the first communication system, otherwise the synchronisation is restarted for the second transport system.

Examples are described herein that relate to a mesh in a switch fabric. The mesh can include one or more buses that permit operations (e.g., read, write, or responses) to continue in the same direction, drop off to a memory, drop off a bus to permit another operation to use the bus, or receive operations that are changing direction. A latency estimate can be determined at least for operations that drop off from a bus to permit another operation to use the bus or receive and channel operations that are changing direction. An operation with a highest latency estimate (e.g., time of traversing a mesh) can be permitted to use the bus, even causing another operation, that is not to change direction, to drop off the bus and re-enter later.

A transmitter 10B always transmits a signal (data in which a dock is embedded) generated by the serializer 11 to the communication link. The receiver 20B includes a recovery circuit 22, a deserializer 23, a selector 25, and a training signal generator 32. The training signal generator 32 generates and outputs a training signal for frequency synchronization of the recovering operation of the recovery circuit 22. The selector 25 receives the signal from the transmitter 10B via the communication link and receives the training signal output from the training signal generator 32. The selector 25 selects and outputs either the received signal or the training signal according to the level of the lock signal output from the recovery circuit 22.

A transmitter 10B always transmits a signal (data in which a dock is embedded) generated by the serializer 11 to the communication link. The receiver 20B includes a recovery circuit 22, a deserializer 23, a selector 25, and a training signal generator 32. The training signal generator 32 generates and outputs a training signal for frequency synchronization of the recovering operation of the recovery circuit 22. The selector 25 receives the signal from the transmitter 10B via the communication link and receives the training signal output from the training signal generator 32. The selector 25 selects and outputs either the received signal or the training signal according to the level of the lock signal output from the recovery circuit 22.

Systems, apparatuses, and methods for utilizing training sequences on a replica lane are described. A transmitter is coupled to a receiver via a communication channel with a plurality of lanes. One of the lanes is a replica lane used for tracking the drift in the optimal sampling point due to temperature variations, power supply variations, or other factors. While data is sent on the data lanes, test patterns are sent on the replica lane to determine if the optimal sampling point for the replica lane has drifted since a previous test. If the optimal sampling point has drifted for the replica lane, adjustments are made to the sampling point of the replica lane and to the sampling points of the data lanes.

Systems, apparatuses, and methods for implementing asynchronous feedback training sequences are described. A transmitter transmits a training sequence indication to a receiver via a communication channel including a plurality of data lines. The training sequence indication includes a bit sequence to indicate the beginning of a training sequence. The indication includes a transition from a zero to a one at the midpoint of a supercycle of ‘N’ clock cycles in length, followed by a predetermined number of ones. The training sequence indication is then followed by a test pattern. The beginning of the test pattern occurs at the end of a supercycle. The receiver determines if there are any errors in the received test pattern, and then sends feedback to the transmitter that indicates whether any errors were detected. Responsive to receiving the feedback, the transmitter alters delay settings for one or more of the data lines.