March 2021
Installation, Operation and Maintenance Manual
MDE 254 Rev. 1
HART Command Set26
Section 8: HART Command Set
8.1.19 Command #21: Read Unique Identifier Associated
with Long Tag
This command returns identity information about the field device including: the Device Type,
revision levels and Device ID.
Table 62. Request Data Bytes
Table 63. Response Data Bytes
Byte Format Description
0 - 31 Latin-1 Long Tag
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)
Code Class Description
0 Success No Command-Specific Errors
1 - 127 Undefined
Table 64. Command-Specific Response Codes