s7 1200 nil ptr

[alexmcsheffrey]

Hi can anybody advise
i have been doing a program using s7 1200 (first one)and have been downloading testing modyfy for a few days all ok.Now it will not go into run when i try to put it in run the fault light flashes.in the diagnostics buffer it says nil ptr in ob1??? any ideas what this means and how to sort it

 

[504bloke]

Does the program compile ok?

 

[Peter Nachtwey]

Usually that is caused by an un-initialized pointer.