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Chapter 6: RS-422/RS-485 Connections/Operation
These modes support 2 channels (transmit and receive). The pinouts of the DB-9 male connector are given in Table 4.
Table 4: RS-422/485 Pinouts
Name | Description | Direction | DB9M |
| | | Pin |
| | | |
RD(A) − | Receive Data A | Input | 1 |
TD(B) + | Transmit Data B | Output | 2 |
TD(A) − | Transmit Data A | Output | 3 |
GND | Signal Ground | ------ | 5 |
RD(B) + | Receive Data B | Input | 9 |
Connect only to specified pins for proper operation.
2-Wire RS-485 Connections
Fig. 6.1
2-WireRS-485 Mode: Your cables must bridge pins #1 & #3 and pins #2 & #9 in order to receive and transmit. Connect from Pin #2 to Data B(+) of your devices and from pin #3 to Data A(-) of your devices. Make sure your Mode/Jumpers are set, and that the driver Setting for DTR Operation is RS-485 Mode in the Device Manager.
Note that the EIA RS-422 Specification labels data lines with an "A" and "B" designator. Some RS-422 or RS-485 equipment uses a "−" and "+" designator. In most cases, the "A" line is the equivalent of the "−" line and the "B" line is the equivalent of the "+" line. Some device manufacturers may not follow the standard designation for RS-422 or RS-485, using the A connection for “+” and the B for “-“. In such cases, reversing the line pair permits operation.
Documentation Number 3PCIO1-0903 Manual | Chapter 6 | 43 |
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