Modbus Communication
‑35‑
7. Read the DI state.
Convert the DI state address U007 to 7007 based on the conversion rule, and
convert the read value into a binary value. The LSB indicates DI1, the second bit
indicates DI2, and so on.
8. Read the fault code.
Convert the fault code address U045 to 702D and convert the fault subcode address
U046 to 702E based on the conversion rule.
The following figure shows the configuration and the program.
Common Problems and Solutions
The must‑dos are listed as follows:
1. Check the wiring. Check whether the wrong pins are wired as RS485+ and RS485–
incorrectly.
2. Check whether the communication rate defined by FD‑00 of the MD520 is
consistent with that of the host controller.
3. Check whether the data format defined by FD‑01 of the MD520 is consistent with
that of the host controller.
4. Check whether the communication address defined by FD‑02 (local address) of
each device is unique to avoid conflicts caused by duplicated local addresses.
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