SLF1 error on stopping modbus connection

[YorickBM]

Hi All,

Currently, I'm working on a python program that uses serial Modbus to communicate with an ATV320 drive. 

Once my program finishes and the keep-alive ping of every second stops, when the Modbus timeout amount is reached in the ATV320 it will go into SLF1 fault. What do I need todo so it does not go into SLF1 fault? Currently, my program runs the following Modbus sequence:

8501 -> 0x0006 

8501 -> 0x0007

(Startup done)

8502 -> 500 (Set frequency reference of ATV320)

8501 -> 0x040F (Start conveyer belt in reverse altho reverse isn't working?? just keeps going forward)

(Run for a period of time)

8501 -> 0x0007

8501 -> 0x0006

8501 -> 0x0000

8502 -> 0x0000

(keep-alive also stops now, after set Modbus timeout SLF1 error pops up)

[LeoLazzaro]

Hi YorickBM

Sorry I'm not familiar with python program, but PLCs are always writting the CMD (8501) and RFR (8502). The drive recognozes a fault SLF1 when It has not received any package during Time out , then when time out is reached , the drive trigger SLF1. Please try to write this 2 parameters before the time out to keep alive the comunication .For other hand , reverse is 080F hex. Please refer to the Modbus communication manual

https://download.schneider-electric.com/files?p_enDocType=User+guide&p_File_Name=ATV320_Modbus_manua...

Thank you in advance

B.R.

[Ahmed_Alzafer]

Hello,

In fact this is a normal behavior. At first time you write the frequency by Modbus, the drive will begin to monitor Modbus channel, to check that the controller write or read at least one time during the time set in parameter TTO.

Assuming that TTO is set to 30s, then when you write Frequency by modbus, you will have 30s at most to send any read or write request by the controller to the drive before SLF1 fault appears.

This is described on ATV320 Modbus manual:

[YorickBM]

Hey, I know what causes this error to occur since I have read the manuals provided.

For my case it was a question of is there a way to PREVENT this error from occuring if the disconnection is deliberately done. As described in the post I send the commands to turn off the ATV320 (as described in their manual).

Now it basically forces you to use fault reset every time I would reconnect with my program..... How can I prevent the SLF1 error when disconnecting deliberately with the ATV320 after shutdown commands are send described in the manuals.