How do master modules behave when they become optional

Kevin Arscott 7 years ago in IQANdesign updated by Antonio Garcia 3 months ago 8
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.

Hello! Would like to continue this post from some years ago. Gustav, if you prefer it, just tell me or feel free to move this to a new thread.

I think I get the purpose of optional masters. From the manual I found this:

At the moment I'm designing an optional machine attachment which requires a large controller such a MC43. And would like to use this controller instead of an expansion module. While maintaining all the IQAN advangantes related to diagnosis, adjusts, and so on. Due to this, this module would be a new (optional) master on an already existing multi-master system, which consists on another MC43 (headmaster) and a MD4 display.

I understand that the whole system, if the machine has the attachment, must contain the exact same project for running. No problem with this.

And that the base system on a machine with no attachment can run normally and also be upgraded if necessary.

But, lets say I would like to get the project from a machine without attachment. I think that I once tried this, but it was not possible, an error was thown because the system was incomplete. May be getting a clone also fails, not sure.

Retrieving current app or clones from a machine is an essential feature for me. So including an optional master on the system would have this huge handicap when that master is not present? Is it like that? Any workaround?

I have not tested it again. Neither I'm sure if this has been solved at some point...(even if the optional master application is missing from the reconstructed project, that would be better than no project at all! )


Hello Again,

Have been testing this on a recent IQAN version (6.0X). 

Indeed it still fails when trying to get the project from IqanDesign:

And it does not allows to continue without the optional module (During testing the optional module was the MD4), as the project would be uncomplete I suppose.

On Iqanrun, it allows you getting the project on project View, and lets you watching the application logic of the existing modules and start measuring while viewing the app. But you can not save a project copy from iqanrun.

I would like to remark that you can make clones from the existing modules, and upload them back to those modules without problems

Gived it a try opening the clone from IQANdesign, but an error is thrown also due to the lacking optional module:

So, the only missing feature is getting back an editable project from an incomplete system (optional module not present).

I suppose this was a decission intended to guarantee project integrity and IQAN system robustness. Cause getting a partial project (with only the apps from the existing modules) and allowing to open it on IQANdesing, would lead to a different project, with different checksum...so it won't be same project version anymore. Which can become a great mess...

I think I will have to stick to an expansion module. Thanks.