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Using the MSCAN Identifier Acceptance Registers to capture multiple ARB ids

Question asked by dave Klotzbach on Jun 28, 2017

I am using a 9S12XEP10 star12 processor and working with existing code.

I need to capture a range of 7 ARB IDs on a single CAN port. I am having trouble understanding how to use the CANIDAR0-7 and CANIDMR0-7 to make this work. I want to capture all messages in a group that only differ in the 3 lowest bits of the address. ie. 0-7. However, when I try to set them up, I only get the 0.

I am using the Processor Expert because the existing code was written that way, and the Acceptance mode was written for 2 32-bit address and mask register and the code is using  STD and XTD modes. The code works for capturing a single ARB-ID, but I don't seem to have it correct for multiple ARB-IDs. Also, the default MASKs is as follows:

  • STD 0x70007u
  • XTD 0x70000u

What I need to know is:

  1. Why does the '7' appear twice in the STD mask?
  2. For my specific example should STD be 0x3F003Fu and XTD 0x3F0000u?
  3. Should my Identifier value, again for STD,  be (id<<21 | id<<3?) or (id << 21)?