Publication 1769-UM020A-EN-P - December 2009 37
Module Data, Status, and Channel Configuration Chapter 3
Clamping (limiting)
Clamping limits the outputs from the module to within a
user-configured range when the controller commands an output to a
value outside of that range. The module supports a high clamp value
and a low clamp value for each output channel. Once clamps are set
for a module, any data received from the controller that exceeds those
clamp values sets an appropriate over-range and under-range clamp
status bit and transitions the output to that limit but not beyond.
Clamp High and Clamp Low Data Values
Clamping is disabled on a per channel basis for each output channel
by entering a 0 value in both the clamp high data value and clamp
low data value words in the configuration-data file. If either the clamp
high data value or clamp low data value words have a non-zero value
entered, clamping is enabled for the corresponding output channel.
Non-zero clamp data values are considered valid only if they are
within the full-range limits set by the type/range and data format
selections for the channel. Also, the non-zero clamp data values are
valid only if the high clamp data value for an output channel is greater
than or equal to the low clamp data value.
Latch Clamp Status (LC)
If the selection is enabled (LC = 1), the module latches any over-range
or under-range clamp status bits that are set in the Input Data file.
Latched clamp status bits must be reset via the Output Data file. If the
selection is disabled (LC = 0), any clamp status bits that are set in the
Input Data file are automatically reset when the clamp limits are no
longer exceeded by the controller. The default setting is disabled.
Enable Low Clamp Alarm Interrupt and Enable High Clamp Alarm Interrupt
(ELI and EHI)
If the selection is enabled (ELI = 1 or EHI = 1), the module generates
a module interrupt to the controller when an over-range or
under-range clamp status bit is set (1). A separate interrupt can be
enabled for each output channel’s high clamp status and low clamp
status. If the selection is disabled (ELI = 0 or EHI = 0), no module
interrupts are generated when output clamp status bits are set. The
default setting is disabled.
TIP
N
Not all controllers support module interrupts and this function.
Refer to your controller’s user manual for details.
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