Rockwell Automation T7491 ICS Regent+Plus Mixed I/O Modules - Manual (Page 8)

Multiplexed I/O Module (T7491)
8
Industrial Control Services
When output data changes state, the Mux I/O module writes
the output data to both ports. At the MIU processor, the
output data is 2oo2 voted, so that when the data agrees, the
outputs are updated.
When input data disagrees, the Mux I/O module reads the
input data three more times. If the disagreement persists, a
failure is reported.
Serial Port Cable Connections
The serial communications cables are connected to the
connector terminals located on the rear of the I/O chassis slot
where the module is installed. Figure 4 illustrates the proper
connections for the serial ports.