MAX CAN logfile missing bits?

[nmholmgren]

I am using the Measurement & Automation Explorer as a Bus Monitor for a CAN bus (using a PXI-8464 module in a PXI-1036 chassis, connected via two PXI-8331 cards to a PC), with all messages logged to a file in comma-separated values (.CSV) format. The first field of each record in the logfile is labeled "Arb ID.". The contents of the data in that field are apparently the 11-bit standard identifier concatenated with the 18-bit extended identifier (I'm using extended format messages). One other odd thing: each value in that field has an asterisk at the end of it.

Q1: What happened to the other 3 bits of the arbitration ID (SRR, IDE, and RTR)?

Q2: What does the asterisk mean?

[Chris_R.]

Hi nmholmgren,

The SRR, IDE, and RTR are not part of the Arbitration ID.  What do you see missing? 

The * simply means that an extended Arbitration ID is used.  An "R" showing means a remote frame is used.  For more details on the Bus Monitor, you can also click the "Help" button within the Bus Monitor.

Have a great day!

[nmholmgren]

I think I see the problem. The CAN 2.0 spec doesn't actually define "Arbitration ID". It defines (section 3.2.1) "Arbitration Field", which includes "Identifier", "RTR Bit", "SRR Bit", and "IDE Bit". I interpreted the logfile's heading of "Arb. ID" to mean "Arbitration Field". Per your message, the correct interpretation is "Identifier".

BTW, I had searched the MAX help, it didn't help.

Thanks,

Neil Holmgren

Avtech