Installation guide

Introducing the Modbus Plus Network

890 USE 100 00

1.13 Bridging Modbus Plus and Serial Devices

1.13.1 How the Bridge Multiplexer Operates

The BM85 Bridge Multiplexer device operates as a standard Modbus

Plus node, receiving and passing tokens in the network’s address

sequence. It provides four serial port connections to allow Modbus Plus

nodes to communicate with serial devices. BM85 models are available

for support of Modbus, RS232, and RS485 serial devices.

1.13.2 Modbus Configurations

Each Modbus port can be configured to support a master device, slave

device, or a network of up to 32 slave devices. Selection of ASCII or

RTU mode, baud rate, parity, stop bits, link timeout value, and function

code conversion is also configurable.

Figure 22 illustrates four types of Modbus devices connected to a

Bridge Multiplexer.

MODBUS PLUS NETWORK (UP TO 64 NODES)

BM85

BRIDGE

MULTIPLEXER

CPU

P230

PROGRAMMING

IBM PC

J478

MODBUS

= MODBUS PORT

PANEL COMPATIBLE

MODEM

(SLAVE)

1 2 3 4

MODBUS NETWORK

1 ... 32 DEVICES

(MASTER) (MASTER)

CPU

CPUCPU

Figure 22 Modbus Devices Multiplexed to Modbus Plus