HART Multiplexer System KFD*-HM*-16
Configuration
2018-04
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6.7.4 Command Caching Function
Cyclical Data Retrieval
With cyclical data retrieval, the HART multiplexer master periodically retrieves data from the
connected field devices and stores the data in its internal memory.
If the process control system queries the data of the field devices, this data can be forwarded
more quickly. The data is no longer read directly from the field device. Instead, it is read
directly from the memory of the multiplexer master. See chapter 6.7.3.
Displaying the Command Caching Function Settings
1. Use the mouse to double-click the multiplexer master KFD2-HMM-16 in
the project window.
2. In the editing window, open the Configuration > Command caching menu.
The Command caching window is displayed.
3. Click Apply to confirm your selection.
4. Select Revert to reset your selection.
The command parameters for the multiplexer master are displayed and set in the
Command caching menu:
• Mode: This switches the Command caching function on or off.
• Disabled: The function is switched off.
• Default caching: The function is switched on. This is the default setting.
The commands selected are cached, see below.
• HART command: Here you can use a drop-down menu to select which values are to
be read out from the field devices:
• Command1-ReadPrimaryVariable: Only the primary variable of the field device
is read out.
• Command2-ReadLoopCurrentandPercentOfRange: The current value in mA
is read out.
• Command3-ReadDynamicVariablesandLoopCurrent: All variables of
the field device are read out.
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