1.5 s5: Multi-coordinator PLCA action

Description

When operating as a PLCA Coordinator, if the PHY receives an unexpected BEACON from an additional coordinator on the segment, it will set the Unexpected BEACON Received (UNEXPB) bit in the Status 1 (STS1) register. The PHY will then enter a recovery state in which it can receive packets but will transmit neither packets nor BEACONs for the next two PLCA bus cycles. Should the duplicate Coordinator continue sending periodic BEACONs, then the PHY will remain in the recovery state unable to transmit to avoid collisions with the duplicate Coordinator in Transmit Opportunity 0.

Clause 148 of IEEE Std 802.3™ describes that when this condition occurs, the PHY should avoid transmitting in its transmit opportunity until the end of the current bus cycle when the PHY will again transmit its BEACON to the segment.

End User Implications

The PHY will halt transmitting packets and BEACONs to the network when configured as a PLCA Coordinator and an unexpected BEACON is detected. This results in the node becoming an inactive Coordinator.

Work Around - Revision C2 and earlier

The station management entity should monitor the Unexpected BEACON Received bit and configure the PHY as a PLCA Follower.

Work Around - Revision D0

As of revision D0, this silicon errata may be resolved with the register configuration provided in the table below.