Confirming the Unit Settings and Design ContentsFP2 Serial Data Unit
3 − 3
3.1 Signals of RS232C Connector
3.1 Signals of RS232C Connector
RS232C
RS232 is a set of serial communication standards compiled by the EIA (Electronics
Industry Association). Originally, RS232 served as an interface for connecting personal
computers, modems, and other devices, but currently it is widely used as a
general−purpose interface for PLCs and other control devices. Most commonly, it is
used as a 25 −pin or 9−pin D−Sub connector, and the purposes and timings of the
various signal lines are regulated by the standards.
Pin layout
Pin No. Name Abbrev. Signal direction
1 Protective ground FG —
2 Sent data SD Unit → External device
3 Received data RD Unit ← External device
4 Request to send RS Unit → External device
5 Clear to send CS Unit ← External device
6 Not used — —
7 Signal ground SG —
8 Received line signal detector CD Unit ← External device
9 Data terminal ready ER Unit → External device
FG (Protective ground)
With the serial data unit, this is connected to the FG terminal of the power supply unit
through the FP2 backplane, along with the D sub−connector housing.
SD (Sent data)
This is the signal line used when data is sent to the other side. With the serial data unit,
the SD (green) LED of the operation status display LED blinks when data is being sent
normally.
RD (Received data)
This is the signal line used when data is received from the other side. With the serial
data unit, the RD (green) LED of the operation status display LED blinks when data is
being received normally.
RS (Request to send)
This is the signal line that requests data to be sent from the other side.
With the serial data unit, the RS signal is normally on.
CS (Clear to send)
This signal line is on when data can be received by the other device. With the serial data
unit, data cannot be sent until an on signal is received from the other device. If this signal
line is not connected to the other device, it should be connected to the RS (Request to
Send) of the serial data unit.
SG (Signal ground)
This signal line provides a common reference potential for the various mated circuits
connected to each other in the serial data unit and peripheral devices.
1
2
345
6789
(9 pins)
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