March 2021
Installation, Operation and Maintenance Manual
MDE 254 Rev. 1
HART Command Set14
Section 8: HART Command Set
Code Class Description
0 Success No Command-Specific Errors
1 - 127 Undefined
Table 9. Command-Specific Response Codes
8.1.2 Command #1: Read Primary Variable
This command returns the Primary Variable value with its Unit Code. The Primary Variable (PV) is the
percentage corresponding to the Loop Current signal.
Table 10. Request Data Bytes
Byte Format Description
None
Code Class Description
0 Success No Command-Specific Errors
1 - 5 Undefined
6 Error Device-Specific Command Error
7 Undefined
8 Warning Update Failure
9 - 15 Undefined
16 Error Access Restricted
1 - 127 Undefined
Byte Format Description
0 Enum Primary Variable Unit Codes (see Section 8.4, Table 120)
1 - 4 Float Primary Variable
Table 11. Response Data Bytes
Table 12. Command-Specific Response Codes
Byte Format Description
0 Unsigned-8 "254" – Fixed Value
1 - 2 Enum Expanded Device Type Code (see Section 8.4, Table 119)
3 Unsigned-8 3 = Minimum number of preambles required for the request message from the Master
to the Slave
4 Unsigned-8 7 = HART Protocol Major Revision
5 Unsigned-8 Device Revision
6 Unsigned-8 Software Revision
7 Unsigned-5 MSB (5 bits) – Hardware Revision
7 Enum LSB (3 bits) – Physical Signaling Code (see Section 8.4, Table 126)
8 Bits Flag Assignement (see Section 8.4, Table 127)
9 - 11 Unsigned-24 Device ID
12 Unsigned-8 Minimum Number of preambles to be sent with the response message from the Slave
to the Master.
13 Unsigned-8 Maximum Number of Device Variables.
14 - 15 Unsigned-16 Configuration Change Counter
16 Bits Extended Field Device Status (see Section 8.4, Table 129)
17 - 18 Enum Manufacturer Identification Code (see Section 8.4, Table 124)
19 - 20 Enum Private Label Distributor Code (see Section 8.4, Table 124)
21 Enum Device Profile (see Section 8.4, Table 134)
Table 8. Response Data Bytes
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