Rockwell Automation T7491 ICS Regent+Plus Mixed I/O Modules - Manual (Page 7)

Multiplexed I/O Module (T7491)
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Active and Fault Status Indicators
These green and red LEDs indicate the overall health of the
MUX I/O module. During normal operation the green
ACTIVE indicator flashes at the controller's scan rate. If a
fatal module fault is detected the red FAULT indicator
switches on and the green indicator switches off. Refer to page
4 for descriptions of fatal module faults.
Port Status Indicators
Both of the multiplexed I/O module’s ports have transmit,
receive and communications fault status indicators.
The green TX and RX indicators turn on and off reflecting
normal transmission and reception of communications data.
The communications fault indicator is normally off. When a
non-fatal communications fault occurs, the red LED switches
on. Refer to page 4 for descriptions of non-fatal faults.
Application
Simplex Configuration
Most often the Mux I/O module is used in simplex
configuration. In this configuration, each of the two serial
ports are used to individually connect to MIU equipment. The
module uses the downloaded configuration information to
read inputs and write outputs for each serial port.
Dual Configurations
To protect against communications failures related to the
serial cables, the module can be configured for duplex
operation. When configured this way, the Mux I/O module
communicates to the connected equipment by reading from
and writing to both communications ports. Each port is cabled
to the same MIU processors.
The Mux I/O module reads inputs from each port and stores
the information in separate areas in RAM. The RAM data is
2oo2 voted, so that when both data areas agree, the input data
is updated for the Regent processor modules.