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Chapter 5: RS-232 Connections/Operation
The
Table 3: RS-232 Pinouts
Name | Description | Direction | DB9M |
|
| (DTE) | Pin |
|
|
|
|
DCD | Data Carrier Detect | Input | 1 |
RD | Receive Data | Input | 2 |
TD | Transmit Data | Output | 3 |
DTR | Data Terminal Ready | Output | 4 |
GND | Signal Ground | 5 | |
DSR | Data Set Ready | Input | 6 |
RTS | Request to Send | Output | 7 |
CTS | Clear to Send | Input | 8 |
RI | Ring Indicator | Input | 9 |
RS-232 Operation
The primary
The RTS and CTS signals are Handshaking lines used to indicate to the other device that data can be sent or received. These lines may be enabled or disabled on a
Two secondary Handshaking signals are DTR and DSR. They are usually enabled when the device is powered up and the port is open. They may be used for flow control by some devices instead of RTS and CTS.
DCD is used by a modem to indicate Carrier to the computer so data can be sent/received. RI is output by a modem to indicate that the phone or FAX line has a incoming call, so it can be handled.
Documentation Number | Chapter 5 | 41 |
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