10-6 Serial Port Communications and Commands Date Code 20001006
SEL-351 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 Shielded Ground
RTS Request To Send
CTS Clear To Send
DCD Data Carrier Detect
DTR Data Terminal Ready
DSR Data Set Ready
For long-distance communications up to 500 meters 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 PROTOCOL
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-351 Relay provides standard SEL protocols: SEL ASCII, SEL Distributed Port Switch
Protocol (LMD), SEL Fast Meter, and SEL Compressed ASCII. In addition, the relay provides
MIRRORED BITS™ and Distributed Network Protocol (DNP) V3.00 as ordering options. The relay
Courtesy of NationalSwitchgear.com
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