3-2 Communications Date Code 970103
SEL-251, -2, -3 Instruction Manual
The serial data format is:
Eight data bits
Two stop bits (-E2 model) or one stop bit (-E1 model)
No parity
This format may not be changed.
Figure 3.1 shows the pin number convention for the EIA-232 data ports.
Figure 3.1: 9-Pin Connector Pin Number Convention
Table 3.1 and Table 3.2 list port pin assignments and signal definitions for the conventional
terminal block model and the plug-in connector model, respectively.
Table 3.1: SEL-251 Conventional Terminal Block Model
Relay Serial Port Connector Pin Assignments
Pin
Port 1,
Port 2R Port 2F Description
1 +5 Vdc N/C +5 Vdc available if JMP12 installed
2 RXD RXD Receive data input.
3 TXD TXD Transmit data output.
4 +12 Vdc N/C +12 Vdc available if JMP13 installed
5 GND GND
6 -12 Vdc N/C -12 Vdc available if JMP14 installed
7 RTS RTS The relay asserts this line under normal conditions.
When its received-data buffer is full, the line is deas-
serted, and asserts again when the buffer has sufficient
room to receive more data. Connected devices should
monitor RTS (usually with their CTS input) and stop
transmission whenever the line deasserts. If transmis-
sion continues, data may be lost.
8 CTS CTS The relay monitors CTS, and transmits characters only
if CTS is asserted.
9 GND GND Ground for ground wires and shields
(female chassis connector, as viewed from outside panel)
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