Appendices
A-12
CJ-series PROFIBUS Master Unit Operation Manual for NJ-series CPU Unit (W509)
A-3 Application Notes
This appendix contains an application note regarding the use of a special ladder program to detect any
CJ1W-PRM21 PROFIBUS Master Unit failures. This programs specifically covers failures due to faulty
bus parameters, set by the user.
The CJ1W-PRM21 Master DTM allows the user to change certain bus parameter, in order to further
optimize the PROFIBUS network performance. The risk however in doing this is that certain combina-
tions may lead to failures in the communication, either direct, or at a later point in time. The direct result
of this failure is that communication between the Master Unit and the CPU - the CPU I/O refresh cycle -
will take longer than anticipated.
A ladder program can now be used to detect this, if the application warrants this safety measure. It
relies on the fact that non-used software switches (see section 4-2-1 Software Switches (*_SwCmd))
when set by the user program, are always reset by the Master Unit.
Application Note Background
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