Installation guide

2 Introducing the Modbus Plus Network
890 USE 100 00
1.1 Introducing the Modbus Plus Network
1.1.1 Modbus Plus Applications
Modbus Plus is a local area network system for industrial control
applications. Networked devices can exchange messages for the control
and monitoring of processes at remote locations in the industrial plant.
Modicon products supporting Modbus Plus communication include
programmable controllers and network adapters. The network is also
supported by a variety of products from other manufacturers.
Each Modicon controller can connect to Modbus Plus directly from a
port on its front panel. Additional networks can be accessed through
Network Option Modules (NOMs) installed in the common backplane.
The network also provides an efficient means for servicing input/output
subsystems. Modicon Modbus Plus Distributed I/O (DIO) Drop
Adapters and Terminal Block I/O (TIO) modules can be placed at
remote I/O sites to allow the application to control field devices over the
network link.
1.1.2 Extending the Network
Each network supports up to 64 addressable node devices. Up to 32
nodes can connect directly to the network cable over a length of 1500 ft
(450 meters). Repeaters can extend the cable distance to its maximum
of 6000 ft (1800 meters) and the node count to its maximum of 64.
Fiber optic repeaters are available for longer distances.
1.1.3 Bridging Networks
Multiple networks can be joined through Bridge Plus devices.
Messages originated on one network are routed through one or more
bridges to a destination on another network. Bridges are applicable to
networks in which fully deterministic timing of I/O processes is not a
requirement. In a network requiring deterministic I/O timing,
messages for DIO/TIO nodes are passed on that network only, and do
not pass through bridges.
Modbus and custom RS232/RS485 serial devices can access Modbus
Plus through Bridge Multiplexers. Each Bridge Multiplexer provides
four configurable serial ports. A serial device can communicate with