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Old August 17th, 2011   #2
sblair
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1. A message count must be 0x00 as received by a responder. What if a non-zero value is received, this should generate a format error?
In many respects this is up to you. I generally advocate trying to gracefully handle errors as well as possible. In this case, you could NACK the request message, but from a responder point-of-view it really doesn't care what that field is set to. Yes, the controller is supposed to send 0x00, but you could easily ignore whatever value it sent and and still handle and respond to the message correctly which is what I would suggest.

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2. What error to give with a wrong message class value -> format error?
If you get a message with an invalid COMMAND_CLASS or one that you just don't support for that message, then the correct response would be to NACK with NR_UNSUPPORTED_COMMAND_CLASS

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3. When the packet data length mismatches with data length -> format error?
Depends, if you were able to decode the message and had all the data necessary to handle the message, I'd just go ahead and handle it. Otherwise NR_FORMAT_ERROR would probably make the most sense.

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4. When a PID requested via PARAMETER_DESCRIPTION is not available -> format error or range error?
In this case, NR_DATA_OUT_OF_RANGE is what you should use.
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