Siemens S7 Modbus with Noctra Gebhardt Fans

[Roksan]

A customer site has 26 Nicotra Gebhardt EC PFP roof mounted ventilation fans. Control and monitoring is to be via Modbus RTU withing a Siemens PLC.
I am sequentially reading data OK from the fans with the MB_MASTER function, mode 0, address 30001, data length 33 (Modbus function 04, read input registers 0 to 32).
The write function to the fans is not working with mode 1, address 40067, data length 1 (Modbus function code 06, write holding register 66).
Anybody used these fans with Siemens Modbus and have any suggestions? I've tried Nicotra Gebhardt support, but no suggestions so far.

 

[Puddle]

Try using mode 2? I had errors using mode 1 to write but I can't remember what the issue was.

Is there any preceding logic to your master blocks or are they called simultaneously? It may be causing a conflict.

I never thought of programming the way you have with multiple masters assigned to the same DB, I've just been changing the input values on the same block for every call.

 

[Roksan]

Try using mode 2? I had errors using mode 1 to write but I can't remember what the issue was.

Is there any preceding logic to your master blocks or are they called simultaneously? It may be causing a conflict.

I never thought of programming the way you have with multiple masters assigned to the same DB, I've just been changing the input values on the same block for every call.

Thanks for the reply. I have tried mode 2, with the same result. And yes, there is preceding logic to sequence the read/write operations so that there is only ever one read or write command active at any one time.

 

[Lare]

Try to sequence also EN input of block.

Also modbus query is several program cycles long so you need also time period between different read and write commands.

 

[Roksan]

Try to sequence also EN input of block.

Also modbus query is several program cycles long so you need also time period between different read and write commands.

Thanks for the reply. The ‘REQ’ flag to request each read/write operation remains on until either the DONE OR THE ERROR status bit is returned by the read or write operation. I have also setup a test block with just one write operation called, and have tried using the same bit that is used for the write request to energise the Modbus block enable. Same result.