Momentum Modbus Plus 170 PNT Series Guía de usuario descargar pdf (Pagina 131)

Using the Modbus Plus Ports

870USE10110 July 2004 131

Two Types of Modbus Plus Networks for Momentum Components

I/O Networks and

Supervisory

Networks

In a distributed control environment, Modbus Plus can be used in either of two ways:

as an I/O network

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.

What if I Need

Both Types?

If your system requires both supervisory and I/O handling architectures, one solution

is to use a processor adapter with I/O bus capabilities as the I/O network and either

a 172 PNN 210 22 or 172 PNN 260 22 option adapter with Modbus Plus for the

supervisory network.

CRITICAL I/O MUST BE SERVICED IN AN I/O NETWORK

For programming, the user interface, and third party Mod Connect devices,

Modbus Plus offers either deterministic I/O servicing or non-deterministic

supervisory servicing.

Design your Modbus Plus architecture to meet the needs of your network.

Do not use a supervisory network to service critical I/O.

Failure to follow this instruction can result in injury or equipment damage.

CAUTION

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.

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Momentum Modbus Plus 170 PNT Series Guía de usuario Pagina 131