Modbus Serial master error56

[V.S]

Dear Friends

I am using modbus library to communicate with an external slave device via modbus RTU. When I run the code it sometimes generates Error56 but sometimes it does not generate any Error and it runs correctly. What is the reason of this Error56? 

Regards

V.S.

[mikeporter]

Momentary glitches, phase of the moon, bad karma resulting from the music file you downloaded last night -- take your pick. On modbus I never accept an error 56 (or 66 either) unless it happens a couple times in a row. The thing to do is drop the connection and try to reconnect.

Mike...