22 • XR75CX I&O Manual 026-1210 Rev 4
18 ECT MODBUS
Networking to
E2s
18.1.COM Port Associations
- E2 Versions 3.xx and
Below
Connecting a XR75CX controller to an E2 requires the E2
to be version 2.84 or above. Contact Emerson for upgrade
information if the controller is a version before 2.84.
An E2 has up to three COM ports that can be assigned for
MODBUS communication: COM2, an RS485 port on the
E2 power interface board, and COM4 and COM6, which
are optional ports requiring expansion cards.
COM4 is
recommended for MODBUS connection of XR75CX units.
COM ports can only be used for one function; in other
words, if COM2 is set up as the I/O network, you cannot
connect MODBUS devices to COM2. Ensure your E2 is
equipped with an RS485 COM Card (P/N 637-4890) and
configured in E2 General Services
(,
Serial tab) to enable COM4 or an E2 Expansion COM
Card (P/N 637-4871) to enable COM6.
Connect the MODBUS network cable to the three-terminal
connector on the COM port you wish to assign as
MODBUS. Reverse polarity of +/- on RS485 cable from
E2 to the device.
18.2.COM Port Associations
- E2 Versions 4.2 and
Above
An E2 has three COM ports that can be assigned for
MODBUS communication (COM2). COM ports can only
be used for one function; in other words, if COM2 is set up
Figure 18-1 - Location of E2 COM Ports (E2 versions 3.xx and
Below)
E2 PIB COM PORT ASSOCIATIONS
COM1
COM4
COM6
COM2
Serial Device
RS485 COM Port
(2 Connectors)
RS485 COM Card
(2 Connectors)
Serial Device
RS232 Port
POWER INTERFACE BOARD
(PIB)
E2 Modem/Expansion
COM Card Mounted
Above PIB
Plug-In
Modem
Card
COM3
E2 Enclosure (Right Side)
RS485
RS232
Figure 18-2 - MODBUS Networking
Figure 18-3 - Location of E2 COM Ports - E2 PIB Board (E2
versions 4.2 and above)
E2
XR75CX
#1
TERMINATED,
BIASED
(ALL 3 JUMPERS
IN UP POSITION)
XR75CX
#1 #2
#3
XR75CX
XR75CX
E2 PIB COM PORT ASSOCIATIONS
RS232 Port
POWER INTERFACE BOARD
(PIB)
E2 Enclosure (Right Side)
COM2 COM6
Serial Device
RS485 COM Ports
Plug-In
Modem
Card
COM3
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