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How to read data from MX EcoDrive frequency converter over Modbus RTU?

MX drives are totally different than Altivar drives. See modbus manual for MX eco drives in the attachment. Page 6 shows all important information and page 16 example with function code 17. If you want only to read parameters from MX eco, (not sending commands), then use function code 3 - read holding registers

The modus request will look: (each byte separated by "-")
Slave address - 16#03 - 16#00 - 16#FA - 16#00 - 16#02 - CRCLow - CRCHi

16#00FA is the address of the status word ZTW and 16#0002 means that 2 words will be read:
ZTW (status word) from address 16#00FA
Fact (actual frequency) from address 16#00FB

If you need to read more data, use another request.
Full request and response with function code 3 shown on page 32