Dov Ss Simens

[Eustacio Gadit]

Noticeon the same document the first few pages show the control word STW. This is used to control/ turn the motor on and off. The register for this is shown on the other document (Inverter manual) if you scroll to the register table page 178. it requires that you send Hex 47E (get ready) then Hex 47F (Run motor). (More info on STW Page 17 modbus example).

i understand writing to registers, however for safety i think the inverter needs a constant modbus connection. Should connection fail the motor turns off. This is (im guessing) what simens means by cyclic communication and is not described in depth in the manual (not really designed for labVIEW) "All drives of the port are to be operated cyclically, one after the other." page 7 inverter manual

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If it helps, there is no such thing as a Modbus connection or an RS485 connection, assuming that you are thinking about it in terms of a TCP connection. A tcp connection is a structure in memory that describes the tcp state machine. Modbus over 485 has no such state machine and thus no connection. The only thing that might exist would be a watchdog on the device side, which must be touched at a periodic rate in order to avoid the system going to a safe state. It looks like you want to set 40001 (holding register 0x01) to a value of 0 to disable the watchdog timer.

The error you got is simply modbus error code 4 -- meaning communication is working, and the device is responding to your request saying "I have a fault". Have you read back any of the alarm or fault registers (desc on pg 322) to see what they say? Page 175/76 says its one of:

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