Chapter 5: Communications
21
RS485
Use RS485 to create a multi-drop network containing up to 32 devices.
Table 2: RS485: Pinout
Diagram Pin Number Function
1 A signal (+)
2 (RS232 signal)
3 (RS232 signal)
4 (RS232 signal)
5 (RS232 signal)
Pin #1
6 B signal (-)
Note that when a port is set to RS485, both RS232 and RS485 can be used simultaneously if
flow control signals DTR and DSR are not used.
• Note that the ports are not isolated. If the controller is used with a
non-isolated external device, avoid potential voltage that exceeds
± 10V.
To avoid damaging the system, all non-isolated device ports should
relate to the same ground signal.
Caution
• Use shielded, twisted pair cables.
• Minimize the stub (drop) length leading from each device to the bus.
• Ideally, the main cable should be run in and out of the network
device.
• Do not cross positive (A) and negative (B) signals.
Positive terminals must be wired to positive, and negative terminals
to negative.
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