7.4
SEL-787 Relay Instruction Manual Date Code 20081022
Communications
Communications Interfaces
Autonegotiation, Speed, and Duplex Mode
Single or dual copper Ethernet ports are capable of autonegotiating to
determine the link speed and duplex mode. This is accomplished by setting the
NETASPD and NETBSPD (network speed) to AUTO. Single or dual copper
ports can also be set to a specific speed to be able to apply them in networks
with older switch devices. However, the speed setting is ignored for fiber
Ethernet ports. The single and dual fiber Ethernet ports are fixed by the
hardware to work at 100 Mbps and full duplex mode.
NETPORT Selection
The NETPORT setting gives the user the option to select the primary port of
communication in failover or fixed communication modes. Selecting “D” for
this setting disables both the ports there by providing the user the security to
turn off the ports even if the ports are physically connected to the network.
IRIG-B
One physical interface, serial Port 3 (EIA-232 option only), is provided for the
demodulated IRIG-B time-code input. Another physical interface is via
terminals (B01 and B02), when the relay is ordered with Port 3 as an EIA-485
serial port. When using serial Port 3, connect to an SEL communications
processor with cable C273A (see the cable diagrams that follow in this section
or that are shown in the SEL-5801 Cable Selector software).
+5 Vdc Power Supply
Serial port power can provide as much as 0.5 A total from all of the +5 Vdc
pins. Some SEL communications devices require the +5 Vdc power supply.
This +5 Vdc is available in any combination of Pins 1, 3, and 7 without the
need for hardware jumpers.
Connect Your
PC to the Relay
The front port of the SEL-787 is a standard female 9-pin connector. You can
connect to a standard 9-pin computer port with SEL cable C234A; wiring for
this cable is shown in Figure 7.2. SEL cable C234A and other cables are
available from SEL. Use the SEL-5801 Cable Selector software to select an
appropriate cable for another application. This software is available for free
download from the SEL website at www.selinc.com.
For best performance, SEL Cable C234A should not be more than 15 meters
(50 feet) long. For long-distance communications and for electrical isolation
of communications ports, use the SEL family of fiber-optic transceivers.
Contact SEL for more details on these devices.
Port Connector and
Communications
Cables
Figure 7.1 shows the front-panel EIA-232 serial port (PORT F) DB-9 connector
pinout for the SEL-787.
Figure 7.1 EIA-232 DB-9 Connector Pin Numbers
5 4 3 2 1
9 8 7 6
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