Date Code 20011205
Serial Port Communications and Commands
10-5
SEL-311B Instruction Manual
Table 10.3: Serial Communications Port Pin/Terminal Function Definitions
Pin Function
Definition
N/C No
Connection
+5 Vdc (0.5 A limit)
5 Vdc Power Connection
RXD, RX
Receive Data
TXD, TX
Transmit Data
IRIG-B
IRIG-B Time-Code Input
GND Ground
SHIELD
Grounded Shield
RTS
Request To Send
CTS
Clear To Send
DCD
Data Carrier Detect
DTR
Data Terminal Ready
DSR
Data Set Ready
For communications up to 80 kilometers and for electrical isolation of communications ports, use
the SEL-2800 family of fiber-optic transceivers. Contact SEL for more details on these devices.
C
OMMUNICATIONS
P
ROTOCOLS
Hardware Protocol
All EIA-232 serial ports support RTS/CTS hardware handshaking. RTS/CTS handshaking is not
supported on the EIA-485 Serial Port 1.
To enable hardware handshaking, use the
SET P
command (or front-panel SET pushbutton) to
set RTSCTS = Y. Disable hardware handshaking by setting RTSCTS = N.
If RTSCTS = N, the relay permanently asserts the RTS line.
If RTSCTS = Y, the relay deasserts RTS when it is unable to receive characters.
If RTSCTS = Y, the relay does not send characters until the CTS input is asserted.
Software Protocols
The SEL-311B Relay provides standard SEL protocols: SEL ASCII, SEL Distributed Port
Switch Protocol (LMD), SEL Fast Meter, SEL Compressed ASCII, and M
IRRORED
B
ITS
™. In
addition, the relay provides Distributed Network Protocol (DNP) 3.00 as an ordering option. The
relay activates protocols on a per-port basis. The SEL-311B Relay is compatible with the
SEL-DTA2 Display Transducer Adapter. See Settings Sheet 23 in
Section 9: Setting the Relay
.
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