Rockwell Automation 1794-OF8IH FLEX Isolated Input/Output HART Analog Modules - Manual (Page 23)

Publication 1794-UM065B-EN-E - September 2010
Configurable FLEX I/O Analog Module Features 11
Latch Mode
Latch Mode determines channel operation under wire-off or lead-break fault
conditions. This feature is available for each channel. Channel detection occurs
on a continuous basis. If a fault is detected, the channel fault alarm is set.
If Latch mode is enabled when a fault occurs, the fault will remain latched in
its fault state until a Global Reset (see below) is issued. If Latch mode is
disabled when a fault occurs, the channel reports a fault until the fault is
corrected. Global Reset is not necessary if Latch mode is disabled.
When using your programming software, set the Latch mode bit to 0 to disable
the feature. Set the bit to 1 to enable it.
Global Reset
Global Reset works in conjunction with Latch mode during fault conditions. If
Latch mode is enabled and a fault condition occurs, the channel operating with
a fault remains in this condition (with analog or digital fault state implied) until
a Global Reset is issued. The Global Reset feature resets all outputs of a
particular channel group to accept normal system output data.
The Global Reset feature is an edge triggered signal. Use your programming
software to set the Global Reset bit to 1 for normal operation. Resetting of
outputs occurs during the 1 to 0 transition.
Data Format
You must choose a module data format in your user program. Refer to
1794-OF8IH Data Formats for an explanation of each bit. Data Formats 2, 5,
6, 8, 9, 10, 11, 12, 13 and 15 are not assigned.
When choosing a data format, remember the following:
• If an unassigned Analog Data Format is selected, the module sets
Diagnostic Data to 2 for configuration failure and puts affected
channels in the corresponding fault state.
• An unconfigured module channel can be assumed to have the default
configuration Analog Data Format 0, 0 to 20 mA and Analog Mode
Fault State minimum range. If a non-assigned format is selected, then
the diagnostic 2 for configuration failure is set and the module channel
goes to the default fault state minimum range.