KROHNE UFC 500 HART - Manual (Page 12)

HARTô Smart Communications Protocol
UFC500 Command Specification Rev: 2.0 Release Date: 9 Jun 2001
© 2001 KROHNE Mefltechnik D-47058 Duisburg Page 12
7. Additional Common-Practice Command Specifications
The UFC500 implements a subset of the Common-Practice Commands. This section contains information pertaining to
those commands that require clarification.
7.1 Command #33 Read Transmitter Variables
Multiple transactions are supported: bus master can request from 1 to 4 Transmitter Variables (with codes 0..7) in
arbitrary set.
7.2 Command #34 Write Primary Variable Damping Value
The UFC500 will accept any IEEE value in the range 0.04 to 3600 seconds for the damping value.
7.3 Command #35 Write Primary Variable Range Values
Despite of the actual Primary Variable assignment (FlowRate, TransitTime, Direction), this command always handles
only the FlowRate range specifiers for forward flow. Similar parameters for TransitTime and reverse flow are
controlled via Commands #158/#159, Read/Write Transmitter Variable Range Values.
Upper Range Value is rejected if it exceeds the Upper Sensor Limit or is below the Lower Sensor Limit (both Limits are
available via Command #14). Rejection reason in these two cases is reported via predefined response codes, namely by
code 11, Upper Range Value too High, or by code 12, Upper Range Value too Low. However, it might happen that a
correct Upper Range Value for a given sensor causes the necessity to update the PulseValue variable of the instrument
that plays the role of Upper Range Value for FlowRate measurements, when the latter are mapped onto the
frequency/pulse output. PulseValue upper limit is based on the value of Primary Variable Upper Range. Besides, the
reverse flow can be scaled with its own Upper Range, though it cannot exceed the Primary Variable Upper Range. To
handle correctly these situations, the predefined set of response codes for Command #35 was augmented by the
following multi-definable warnings:
112, Pulse Value Exceeded Max and Was Corrected
113, Pulse Value Surpassed Min and Was Corrected
114, Reverse Range Exceeded Max and Was Corrected
115, Reverse Range Surpassed Min and Was Corrected
Note, that each subsequent correction carried out overrides the reported response code. At first Reverse Range is
checked. Therefore if response codes 114/115 are registered then only the updated Reverse Range should be reread from
device. For response codes 112/113 both Pulse Value and Reverse Range should be reread though the last variable
could remain unchanged.
For additional information refer to Command #142, Read Pulse Output Parameters.
Lower Range Value is always assumed to be zero for UFC500. Therefore this parameter in request packet is ignored.
Transmitter returns zero value in response telegram without prompting master via special response code.
7.4 Command #44 Write Primary Variable Units
Despite of the actual Primary Variable assignment (FlowRate, TransitTime, Direction/ErrorIndication or Off), this
command always handles only the FlowRate units: TransitTime variable has a fixed unit and the rest have none.
The Primary Variable Unit Codes accepted by transmitter include all the HCF units for volumetric flow except the ones
for gaseous media, and are listed in Table 9.1.
As soon as transmitter supports incomparably enlarged unitsí set as opposed to the instrumentís display module, the
impact on the device remote/direct control is straightforward and as follows: transmitter units are made completely