8-6
Serial Port Communications and Commands
Date Code 20010731
SEL-352-1, -2 Instruction Manual
Table 8.3: Serial Communications Port Pin Function Definitions
Pin Function
Definition
N/C No
Connection
+5 V dc
5 V dc 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
C
OMMUNICATIONS
P
ROTOCOL
This section explains the serial port communications protocol used by the SEL-352 Relay. You
set and operate the SEL-352 Relay via the serial communications ports.
Note:
In this document, commands you type appear in bold/upper case:
SET
. Keys you press
appear in bold/upper case/brackets:
<ENTER>
.
Relay output appears boxed and in the following format:
EXAMPLE: BUS B, BREAKER 3 Date: 02/01/93 Time: 00:03:25.180
The communications protocol consists of hardware and software features.
Hardware Protocol
The following hardware protocol is designed for manual and automatic communications.
1. If the SET P setting “RTS_CTS” = N, RTS will always be asserted.
2. If the SET P setting “RTS_CTS” = Y, RTS asserts while the communications buffer is less
than 87 percent full, and RTS deasserts when the communications port buffer is greater than
87 percent full.
3. If the SET P setting “RTS_CTS” = Y, the relay does not send characters until the CTS input
is asserted.
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