7-6
Serial Port Communications and Commands
Date Code 20020129
SEL-387E Instruction Manual
Table 7.3: Serial Communications Port Pin Function Definitions
Pin Function
Definition
N/C No
Connection
+5 Vdc
5 Vdc Power Connection
+12 Vdc
12 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
CD Carrier
Detect
PWR 5
Vdc
C
OMMUNICATIONS
P
ROTOCOL
This section explains the serial port communications protocol used by the SEL-387E Relay. You
set and operate the SEL-387E Relay via the serial communications ports.
Note:
In this document, commands you type appear in bold/upper case:
STATUS
. Keys you
press appear in bold/upper case/brackets:
<ENTER>
.
Relay output appears boxed and in the following format:
XFMR 1 Date: MM/DD/YY Time: HH:MM:SS.SSS
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 communication 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.
