Maxiflex P3 PAC User Manual
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-© Omniflex
UMM126XR18.pdf
5. I/O Module Management & Scanning Explained
5.1 Number of I/O Modules
5.1.1 Local I/O Modules
The CPUs can access up to 15 local I/O modules. These modules are located on the same
Master Base (plus Expander Base) as the CPU.
In a dual redundant configuration, these modules on the local Base are not accessible by the
other Redundant controller (except by using the Sync Blocks). Use Remote I/O modules for
shared I/O in redundant controller applications
5.1.2 Remote I/O Modules
The CPU can access up to 7 remote I/O Racks.
A Remote I/O Rack consists of a conventional Master (with Expander Base if required) fitted
with a M1248A R2c I/O Scanner module in the CPU position.
To access remote I/O systems from the CPU, install an M1593A Remote I/O Network
Interface module (RIO NIM) into Slot 1 of the Master Base in which the CPU is located. This
RIO NIM is connected to the R2c I/O Scanners via a dedicated Remote I/O network.
The Remote I/O network is based on the Conet/c rugged industrial LAN allowing remote I/O
Racks to be installed up to 10km from the Main Process Automation Controller.
Remote I/O Racks are accessible from both controllers in a dual redundant configuration.
5.2 Automatic I/O Module Identification
The CPU automatically identifies each I/O module installed in a Maxiflex system
– both in the
local I/O Base and in the remote I/O Bases.
This information is used for two purposes:
1. Checking for the presence of the correct I/O modules in a system.
2. Automatic scanning of these I/O modules.
5.3 The I/O Module List
You can configure a P3 CPU with the required list of I/O modules for the system. This list is
called the “I/O Module List”.
The CPU continuously compares the present I/O modules against this I/O Module List, and
reports any discrepancies. This monitoring is independent of any User Program downloaded
to the P3 CPU.
User programs must also be configured with the I/O modules used by the User Program. It is
not necessary to configure ALL of the I/O Modules in your IEC61131 User Program. You
need only configure the modules used in the program. This configuration is done in the
Omniflex ISaGraf Programmer’s Workbench before downloading the User Program to the P3
PAC CPU. This module status is also continuously monitored while the program is running.
All of this module status information is available in the DIT for monitoring by a remote device,
and by indication on the I/O OK LED on the front panel of the CPU (see section 11.7.1).