Schneider Electric Processor Adapter - Manual (Page 183)

Using the Modbus Plus Ports
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Two Types of Modbus Plus Networks
I/O Networks and
Supervisory
Networks In a distributed control environment, Modbus Plus can be used in either of two
ways:
l As an I/O network
l As a supervisory network
I/O Networks In a deterministic I/O network architecture, one CPU services up to 63 Momentum
I/O modules, Terminal I/O modules or other Modbus Plus devices.
Supervisory
Networks In a supervisory architecture, several intelligent processing devices share system
data with each other. Many kinds of devices may be part of the network. You should
be aware of each device’s requirement for access to the network and of the impact
each device will have on the timing of your network communication, especially
when servicing non-critical (and non-deterministic) I/O.
Continued on next page
CAUTION
CRITICAL I/O MUST BE SERVICED IN AN I/O NETWORK
Design your Modbus Plus architecture to meet the needs of your network. Modbus Plus can
offer deterministic I/O servicing or non-deterministic supervisory servicing of programming,
user interface, and third party ModConnect devices. Do not use a supervisory network to
service critical I/O.
Failure to observe this precaution can result in injury or equipment damage.
Note: When a programming panel or other human-machine interface (HMI)
device is used as part of a deterministic Modbus Plus I/O network, it
should be connected via the RS232 port on the CPU, not as a Modbus
Plus node.