| Q: |
I cannot communicate with my RS485 or RS422 devices. What is the problem? |
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| A: |
First verify that the port is configured for 485 or 422 mode. For all products except the RCS/4000 you can check this with the browser interface - Port Status page. When switching from RS-232, a port server reboot is required. Furthermore, the port needs to be opened before the browser will indicate the proper interface.
Assuming that it is correctly configured, the most common RS-485 problem is termination. If the receive lines end at the RCS, then the lines must be terminated with a 100-120 ohm resistor between the A and B receive lines at, or as close as possible to, the connector.
On the RCS/4000 you must check the jumper settings on the board to see how the port is configured. Also, on the RCS/4000, the terminator is already built into the board. Additionally, for devices that use + and - labeling, we assume B to be + and A to be -. |
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Answer Last Updated: June 5, 2008 |
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