Input/Output Modules 79
Chapter 3 System Description
Digital Input Module
The following digital input components are available.
The Digital Input (DI) Module has three independent channels which process all
data sent to the module. An ASIC on each channel scans each input point, compiles
data, and transmits it to the MPs upon demand. Input data is voted at the MPs
before processing to ensure the highest integrity.
The DI Module sustains complete, ongoing diagnostics for each channel. If the
diagnostics detect a failure on any channel, the Fault indicator is activated, which
in turn activates the system alarm. The Fault indicator points to a channel fault, not
a complete module failure. The DI Module is guaranteed to operate properly in the
presence of a single fault and may continue to operate properly with certain
multiple faults.
The DI Module continuously verifies the ability of the system to detect transitions
to the opposite state. The DI Module supports hot sparing for online replacement
of a faulty module or continuous back-up to an active module. The DI Module is
mechanically keyed to prevent improper installation in a baseplate.
Model Description Voltage Type
3301 Digital Input Module 24 V DC Commoned
2301 Digital Input Baseplate Direct Termination
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