Packet Error Rate Counters
The Packet Error Rate Counter is in charge of tracking the rate of packet errors per SynqNet cycle. If the Packet Error Rate reaches the FAULT limit, the network will attempt a SynqNet Fault Recovery (for Ring topology only). If the Packet Error Rate reaches the FAIL limit, the network will shutdown. There are Packet Error Rate Counters on the node and controller, which check packets on the upstream and downstream cycle.
The Packet Error Rate Counter also features a "pessimistic" counter function for the fault recovery and failure logic, which increments by one for every packet error received, and decrements by one for every 16th valid packet received. This provides a tolerance buffer on the network, which allows packets to be missed without having to shutdown all communication.
Therefore, if only 1 packet in 100 is bad, the counter will occasionally increment to 1 and then decrement back to zero. If 1 packet out of 10 is bad, the counter will gradually increment until fault and/or fail thresholds are reached. If communication fails completely, the Packet Error Rate Count will match the number of packets lost. The counter is an unsigned 8-bit value, and saturates at 0xFF. It is reset to zero after a hardware reset or can be manually reset in Motion Console. The counter saturates at 255 (0xFF).
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