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Using the Modbus Ports
110
870 USE 101 00 V.3
Modbus Port 2
Two Types of
Port
Modbus Port 2 is available in two types:
Features of an
RS485 Port
Modbus Port 2 can be configured as an RS485 port. RS485 supports two-wire or
four-wire cabling. A multimaster/slave system must use two-wire cabling. A single
master/slave system may use two- or four-wire cabling.
The RS485 protocol handles messaging over long distances with higher level of
noise immunity than RS232 without the need for modems.
Limit of Two
Modbus Ports
The Momentum M1 Processor Adapters can support a maximum of two Modbus
ports.
If a 172JNN 210 32 Serial Option Adapter is used in conjunction with a
171 CCS 780 00 or 171 CCC 780 10 Processor Adapter, the RS485 port on the
Processor Adapter becomes Modbus Port 2. The port on the Option Adapter
becomes electrically neutral and does not support any communication activities.
(The TOD clock and battery backup system on the Option Adapter continue to
work.)
Continued on next page
Component Type of Port Type of Connector
171 CCS 780 00, and
171 CCC 780 10 and
171 CCC 980 20
Processor Adapters
Built-in, dedicated RS485
port
9-pin D-shell connector
172 JNN 210 32
Serial Option Adapter
User may configure port as
RS232 or RS485*
RJ45 phone jack connector
*If the Option Adapter is combined with the 171 CCS 780 00, or 171 CCC 780 10 or
171 CCC 980 20 Processor Adapter, the Modbus port on the Option Adapter will be
disabled.