If your device does not support a Dynamic or Device Variable, the Universal Command Specification (HCF_SPEC-127 Rev 7.1) Section 6.10 states Command 9 MUST respond accordingly:


"When a Dynamic or Device Variable requested is not supported in the Field Device, then the corresponding Value must be set to "0x7F, 0xA0, 0x00, 0x00" (this is HART NaN); the Status must be set to 0x30, (i.e., Status = "Bad" and Limit = "Constant"); the Units Code must be set to "250" Not Used; and the Device Variable Classification set to "0", Not Yet Classified."


The HART Test System has improved the automated testing of this clause.  Developers may encounter the following failure points in UAL011A: 3210, 3220, 3226, 3227.