Rockwell Automation T3122 ICS Regent Processor Modules - Manual (Page 3)

Processor Modules (T3110, 11, 12, 20, 21, and 22)
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permanent faults as they occur. All faults are recorded in the
system's fault history.
Each processor module contains its own power supply that
converts input power to the logic power levels used by the
internal processor circuits. The failure of one power supply
will only effect one processor module — allowing the other two
modules to continue operating — thus keeping the Regent on-
line by virtue of its majority two-out-of-three voting
architecture.
Programs are stored in on-board battery-backed RAM.
Program instructions are fetched from each processor’s
memory and executed by the processors. Data from inputs are
read from the I/O modules in the I/O assembly. The main
processor coordinates the Regent’s activities and solves the
application algorithms programmed by the user. Outputs are
driven by transmitting data through the processor module’s
I/O processor to the I/O assembly.
Communications between the main processor and the I/O
processor are maintained through shared RAM that is used as
a “mail box” for data transfers between the two processors.
All three processor modules operate independently in lock-
step synchronization with the other two modules,
continuously repeating a scan cycle (Figure 2).
Figure 2. The Regent’s Scan Cycle.
The main processors in each of the three processor modules
run programs and process communications synchronously,