Rockwell Automation 1769-OF4VI Compact I/O Isolated Analog Modules - Manual (Page 51)

Publication 1769-UM014B-EN-P - May 2010
Module Data, Status, and Channel Configuration for the Input Module 3-13
1769-IF4I Process Alarms
Process alarms alert you when the module has exceeded configured high or
low limits for each channel. You can latch process alarms. Process alarms can
generate interrupts. (CompactLogix L43 controllers will be able to support
these interrupts.) Process alarms are set at two user configurable alarm trigger
points:
 Process Alarm High
 Process Alarm Low
Each input channel’s process alarms are controlled by bits in the Configuration
Data file. Enable alarms for a channel by setting (1) the EA bit for that
channel. Set the AL bit (1) for a channel to enable the alarm latching. Set the
EI bit (1) for a channel to enable interrupts on that channel’s process alarms.
Each channel’s process alarm high data value and process alarm low data value
are set by entering values in the corresponding words of the Configuration
Data file for that channel.
The values entered for a channel’s process alarm data values must be within
the normal operating data range as set by the input Data Format selected for
that channel. If a process alarm data value is entered that is outside the normal
operating data range set for a channel, the module indicates a configuration
error.
Alarm Deadband
You may configure an Alarm Deadband to work with the process alarms.
The deadband lets the process alarm status bit to remain set, despite the alarm
condition disappearing, as long as the input data remains within the deadband
of the process alarm.
Alarm Deadbands on page 3-14 shows input data that sets each of the two
alarms at some point during module operation. In this example, latching is
disabled; therefore, each alarms turns OFF when the condition that caused it
to set ceases to exist.