How do master modules behave when they become optional

Kevin Arscott 5 years ago in IQANdesign updated by Gustav Widén (System support) 5 years ago 6
We are using a system with two master modules, MC3 and MD3. I have several questions regarding how the system behaves when disconnected. We are intending on having only the MC3 set as optional as all the fault logging is done within the MD3.

What happens if the can line is disconnected when the system is live? Will we get any errors within the MD3 or notification to say that its been disconnected?

Also we are having an APP out sent to the MD3 to we are able to flag the disconnection of the modules in the MD3. Will the MD3 be able to pick up the APP in has dropped to low after a disconnect? Im assuming we could have a similar setup on the MC3 logic also?


Kevin Arscott.
Hi Kevin, Is it ok to move your question to the public part of the forum and post the reply there?
Making a master module optional with the optional property has some difference compared to making an expansion module optional with the enabled property.

If the IQAN-MC3 is made optional, then the IQAN-MD3 will not flag up any error messages on the screen or write any error to the system log if the MC3 is missing.

The system information channel for Multi master state will show that the system is OK.

But you do get some indication that the MC3 is missing. Any channel values on MD3 display pages that are from the MC3 will show a ' - ' instead of the value.
If you look at values from the MC3 in measure groups on the MD3, you will see that they have status 'No contact'

The most important action is that all the APPIN channels that are coming from APPOUT:s on the MC3 will get the status Timeout, and will change value to the error values set in the applicaiton.

If your MC3 is set as optional and you do want a message about the MC3 being missing, you could use the APPIN status to trigger an error message with e.g. the CMSG channel. This could be a good solution if you have a configurable parameter in the MD3 to say if the MC3 is installed in the machine or not.

Thank for the response. Do I need to restart the system if I reconnect the CAN bus with the system live or will it begin communication again without a restart?
Both APPOUT/APPIN and diagnostics communication will resume again when you reconnect.
The master-master communication always resumes automatically, there is no difference when the master module is optional.

There is one important difference compared to using expansion modules. If you disconnect an expansion module and plug it back in, the communication also resumes aoutomatically. But for the expansion modules, the outputs will need a zero command before they activate again.
If you are using APPIN:s to trigger outputs on a master module, you might want to create a similar check in the application, to avoid unexpected restart of the outputs.