March 2021
Installation, Operation and Maintenance Manual
MDE 254 Rev. 1
HART Command Set18
Section 8: HART Command Set
8.1.8 Command #9: Read Device Variables with Status
This command allows a Master to request the value and status of up to 8 Device or Dynamic Variables.
If the Field Device receives 1, 2, 3, 4, 5, 6, or 7 Request Data Bytes, it returns only the corresponding
number of Device Variables.
Table 28.
No. of Device Variables
Requested
No. of Request Data Bytes No. of Response Data Bytes
1 1 13
2 2 21
3 3 29
4 4 37
5 5 45
6 6 53
7 7 61
8 8 69
Byte Format Description
0 Unsigned-8 Slot 0: Device Variable Code (see Section 9.1)
1 Unsigned-8 Slot 1: Device Variable Code (see Section 9.1)
2 Unsigned-8 Slot 2: Device Variable Code (see Section 9.1)
3 Unsigned-8 Slot 3: Device Variable Code (see Section 9.1)
4 Unsigned-8 Slot 4: Device Variable Code (see Section 9.1)
5 Unsigned-8 Slot 5: Device Variable Code (see Section 9.1)
6 Unsigned-8 Slot 6: Device Variable Code (see Section 9.1)
7 Unsigned-8 Slot 7: Device Variable Code (see Section 9.1)
Byte Format Description
0 Bits Extended Field Device Status (see Section 8.4, Table 129)
1 Unsigned-8 Slot 0: Device Variable Code (see Section 9.1)
2 Enum Slot 0: Device Variable Classification (see Section 8.4, Table 131)
3 Enum Slot 0: Unit Code (see Section 8.4, Table 120)
4 - 7 Float Slot 0: Device Variable Value
8 Bits Slot 0: Device Variable Status (see Section 9.2)
9 Unsigned-8 Slot 1: Device Variable Code (see Section 9.1)
10 Enum Slot 1: Device Variable Classification (see Section 8.4, Table 131)
11 Enum Slot 1: Units Code (see Section 8.4, Table 120)
12 - 15 Float Slot 1: Device Variable Value
16 Bits Slot 1: Device Variable Status (see Section 9.2)
17 Unsigned-8 Slot 2: Device Variable Code (see Section 9.1)
18 Enum Slot 2: Device Variable Classification (see Section 8.4, Table 131)
19 Enum Slot 2: Units Code (see Section 8.4, Table 120)
20 - 23 Float Slot 2: Device Variable Value
24 Bits Slot 2: Device Variable Status (see Section 9.2)
25 Unsigned-8 Slot 3: Device Variable Code (see Section 9.1)
26 Enum Slot 3: Device Variable Classification (see Section 8.4, Table 131)
27 Enum Slot 3: Units Code (see Section 8.4, Table 120)
28 - 31 Float Slot 3: Device Variable Value
32 Bits Slot 3: Device Variable Status (see Section 9.2)
Table 29. Request Data Bytes
Table 30. Response Data Bytes