ERL 8700/BUS, User Manual, Page: 25 / 166

2 Setup and Communications
D01908R02.12 B-PRO User Manual 8700 2-7
Modem Link Unlike a direct serial link, the baud rates for a modem link do not have to be
the same on your computer and on the relay. The modems automatically nego-
tiate an optimal baud rate for their communication.
The baud rate set on the relay only affects the rate at which the relay commu-
nicates with the modem. Similarly, the baud rate set in HyperTerminal only af-
fects the rate at which your computer communicates with its modem. Details
on how to set these respective baud rates are described in “Modem Link - Ex-
ternal” on page 2-3, except that you modify the Port 2 baud rate on the relay
and the properties of the modem in HyperTerminal.
Accessing the SCADA Services
The relay supports DNP3 (Level 2) and Modbus SCADA protocols as a stan-
dard feature on all relays. DNP3 is available through a direct serial link or the
Ethernet LAN on top of either TCP or UDP protocols. The Modbus implemen-
tation supports both RTU (binary) or ASCII modes and is available through a
direct serial link.
The relay’s Port 3 is dedicated for use with Modbus or DNP3 serial protocols.
Port 3 uses standard RS-232 signalling. An external RS-232<->RS-485 con-
verter can also be used to connect to an RS-485 network.
For details on connecting to serial Port 3 see “Communicating with the Relay
(IED)” on page 2-2 and “Communication Port Details” on page 2-8.
The DNP3 protocol can also be run across the optional Ethernet LAN. Both
DNP over TCP and DNP over UDP are supported, for details on connecting to
the Ethernet LAN see “Network Link” on page 2-4.
Complete details on the Modbus and DNP3 protocol services can be found in
“Modbus RTU Communication Protocol” in Appendix E and “DNP3 Commu-
nication Protocol” in Appendix F.
Protocol Selection To select the desired SCADA protocol, login to the relay’s user interface and
access the
Utilities>Setup>SCADA menu. Select the protocol and set the cor-
responding parameters.
Communication
Parameters
Port 3’s communication parameters are set using the Utilities>Setup>Ports
menu in relay’s user interface. Both the baud rate and the parity bit can be con-
figured. The number of data bits and stop bits are determined automatically by
the selected SCADA protocol. Modbus ASCII uses 7 data bits. Modbus RTU
and DNP Serial use 8 data bits. All protocols use 1 stop bit except in the case
where either Modbus protocol is used with no parity; this uses 2 stop bits, as
defined in the Modbus standard.
Diagnostics Protocol monitor utilities are available to assist in resolving SCADA commu-
nication difficulties such as incompatible baud rate or addressing. The utilities
The DNP3 LAN/WAN - TCP and UDP options are only available if the
unit has an optional Ethernet LAN port installed.
Ensure the Master IP Address is different from the relay’s IP Address.
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