Date Code 20010625 Line Current Differential Communications 10-17
and Serial Port Communications and Commands
SEL-311L Instruction Manual
Table 10.4: 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.
COMMUNICATIONS PROTOCOLS
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-311L Relay provides standard SEL protocols: SEL ASCII, SEL Distributed Port
Switch Protocol (LMD), SEL Fast Meter, SEL Compressed ASCII, and M
IRRORED BITS™.
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-311L Relay supports the SEL-DTA2
Display Transducer Adapter analog transducer function with the exception of relay status
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