in reply to: Command 9 Read Device Variables with Status posted by Jens on 06 October 2011 at 13:06:34.
You ask: Does the device check the Device Variable codes in the Request data or does it only count the number of bytes received an then sends the variables 0 - 7?
The field device must look at the actual device variable code values in the command, since they may not be in sequence, or even contiguous. And, of course, the device might have more than just 8 Device Variables, with any set of up to 8 requested.
In your case, if you do not define any Device Variables, yes, you would return PV if a host asks for Device Variable 0, and return the command respose code 14. If a host foolishly asks for further Device Variables, you would return NAN 7F A0 00 00 (see spec for command 9 for more).