March 2021
Installation, Operation and Maintenance Manual
MDE 254 Rev. 1
Device Variables46
Section 9: Device Variables
9.2 Device Variable Status Byte
All cyclical process data include a Device Variable Status byte.
The most significant two bits (bits 7 and 6) of every Device Variable Status byte return the overall
status of the Device or Dynamic Variable value. The next two bits (bits 5 and 4) indicates whether
the Device Variable value is limited. These four bits provide useful status about the Device Variable’s
value. The content of the lower 4 bits depend on the Device Variable Family. Each Device Family can
have its own Device Family-specific Status defining the least significant bits. If set bit 3 indicates the
additional Device Family-specific status is available via the appropriate Device Family Command.
Figure 8
HRT2000v4 doesn’t provide Device Family-specific Status for Dynamic and Device Variables,
therefore last 4 bits are always set to 0.
Device Family-specific Status
More Device Variable Status Available
Limit Status
11 Constant
01 Low Limited
10 High Limited
00 Not Limited
Process Data Status
11 Good
01 Poor Accuracy
10 Manual / Fixed
00 Bad
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