- Software
- IQANdesign
-
Questions
+1
What's the realistic master module limit?
We are planning a project with 6 x MD5 displays and 6 x MC43FS modules, is there a limit that the diagnostic bus and master bus will take before it overloads? These modules are connected all together for both diagnostic and master bus. Conscious of initial start-up bursts and also general running bandwidth consumption.
Customer support service by UserEcho
Well you can only go 0-7 on the ID tags. Pretty sure that's the limit.
We've run an MD4 + 6 XA2s before and it was fine, was definitely annoying to troubleshoot bus failures though.
Thanks, understand the max limit of a given module type but we are running 12 masters on the same master and diagnostic buses (6 x MD5 each with a different ID tags, and 6 x MC43 with different ID tags) so I'm a bit concerned about the max traffic allowed.
If we had multiple masters of different type we could theoretically connect 7 x MC41, 7 x MC42, 7 x MC43, 7 x MC41FS, 7 x MC42FS, 7 x MC43FS plus multiple MD4 and MD5 displays. Not sure a diagnostic or master bus can handle all these connected together even though it satisfies the 0-7 tag rule!
I can only recall seeing one application that has exceeded ten master modules.
We've tested with up to 15, but that is no guarantee that number will work in any application.
The amount of traffic on the Diagnostics bus in a multimeter system will vary with what you show on the IQAN displays. To keep bus utilization at an ok level modules only send values that are currently shown, and the repetition rate is limited. But with more values from other masters presented on the display pages, you will see a higher bus load.
A more general consideration for a system with many CAN nodes is the importance of getting the physical layer right.
With MD5 you will soon be able to run higher bandwidth on the bus, with Configurable speed on diagnostics bus / Software / IQAN. Higher speeds of course give better bandwith, but especially for systems with many CAN nodes that also places a higher demands on getting the wiring right, especially considering stub lines. To be prepared for CAN FD on a system with this many modules you should definitely use MC4x-M24 so you have SiC transceivers on all CAN nodes.