Overview; Troubleshooting The User Defined Can Unit - Omron CJ1W-CORT21 Operation Manual

6 Troubleshooting and Maintenance
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Overview

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Troubleshooting the User Defined CAN Unit

The User Defined CAN Unit uses several error detection and error handling mechanisms.
User Defined CAN is based on the serial bus protocol of CAN. The data link layer of the CAN protocol
combines 5 error detection mechanisms (CRC check, frame check, Ack check, bit check, bit stuffing
check). This combination results in a Hamming distance of 6. This means that at least 6 bits in the mes-
sage frame must have been disturbed to possibly remain undetected. The overall residual error proba-
bility is extremely low and this makes CAN-based protocols very reliable and suitable for harsh
environments.
The User Defined CAN Unit also has manufacturer specific status indication mechanisms
Status
Device Variable *_StaComm indicates the current state of the User Defined CAN Unit communications.
LED Indicators, 7-segment Display
Visual status indication of the User Defined CAN Unit.
Error Log
Some errors are logged in the error log. These errors can be read after a restart.
Startup Sequence
In the following diagram the startup sequence is shown, including the status of all indicators of the unit.
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CJ-series User Defined CAN Unit Operation Manual for NJ-series CPU Unit (W517)