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n601 Modbus data rate is too high

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Hello

If got the warning "n601 Modbus data rate is too high. I have an AKD-P00307-NBCC-I000 with the firmware version M_01-19-00-005.

How I get this warning and how can I avoid it? I couldn't find any parameter for the modbus data rate in the AKD.

 

Best regards

Lukas Köpfli

 
 
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2 Answers

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From the Workbench Help a n601 warning indicates the Modbus data rate is too high ( either the poll rate is too high and/or the number of Modbus read/write requests are too high per poll cycle ).


Key points with a n601 warning:

1) X11 Service port can handle down to 20msec poll rate. Anything lower will overrun the communications buffer. The poll rate is not settable in the AKD; how often the drive is polled ( read or write Modbus requests ) are entirely on the Modbus master side ( typically a PLC or HMI ). If Workbench is running concurrently with the Modbus master this further taxes the Service port.

2) Some potential methods to alleviate the n601 warning are :


a) Increase the poll cycle time ( slow the poll down ) in the Modbus master.

b)Only read or write when you need to. An example is reading a fault. You only need to monitor if a fault exists yes/no and then if yes then query the drive's current faults. Another example is setting up a motion task. This is like a recipe. Typically you'd write the motion tasks for that machine cycle and not put these registers on the poll to be written every scan.

b) Use Dynamic Mapping to organize your parameters and Modbus registers so they are in consecutive order and then you can do block reads and writes instead of individual reads and writes for EVERY parameter. In general it is likely to use a combination of block reads/writes and to also do an individual read or write in an application.

If you are the user and not the designer/programmer of the system I recommend to review this issue with your system integrator or OEM whom you purchased the machine and control from
prior to making modifications.
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Hi Lukas,

The Modbus data rate is always driven by the master, as this is the device requesting a read or sending a write command. Reducing the rate on the master should solve the issue.

The Modbus TXP communication on the AKD is done in the background task. Thus, capacity my vary with other higher priorities tasks and will always have jitter. Make sure to not overload communication and set the pace on the master conservative.

Regards Martin Rupf

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