CRC Error Counters

The Cyclic Redundancy Check (CRC) is a way of detecting small changes in blocks of data. This type of error detection is especially useful when sending packet data across a network such as SynqNet. Whereas the Packet Error Counter checks for missing or invalid packets, the CRC Error Counter checks the validity of the data inside the packets.

Each node has a CRC Error Counter at each port (IN and OUT), although packets are only checked at either the node's IN port or OUT port, depending on where the packets are received.

The controller has a CRC Error Counter at each port (IN and OUT), although packets are checked at the controller's IN port and/or OUT port depending on where the packets are received. For string topologies, packets are received at the controller's OUT port only. For ring topologies, packets are received at the controller's OUT port and IN port, depending on the location of the redundant cable. For example, in a ring topology if the last cable (from the last node to the controller's IN port) is idle, then no data is received at the controller's IN port and the CRC counter at the IN port will remain idle.

The CRC error count will increment by one for bad packets that are addressed to other nodes (or to the controller) or for packets received with a bad CRC. "Lost" packets, which never reach the node, do not increment the CRC error count (it increments the Packet Error Counter). The counters are unsigned, 8-bit values and saturate at a maximum of 255 (0xFF) errors. The counter also goes back to zero after a hardware reset and can be cleared by controller software. Unlike packet errors, CRC errors are NOT node-specific (i.e. All packets are checked at each node, as well as at the controller).

NOTE: Data errors in the start delimiter may prevent the CRC errors from being counted.

In Motion Console

Node CRC Error Counters

In Motion Console, you can see the node's CRC Error Counters in the SqNode Summary Window. It counts the number of upstream CRC Errors for each port.

Controller CRC Error Counters

In Motion Console, you can see the controller's CRC Error Counter in the SynqNet Summary Window. It counts the number of upstream CRC Errors for each port.

See Also

Packet Error Counter
SynqNet Fault Recovery
SynqNet Failure