only one time execution

hi all
i have application which i need on it this condition:

when shutdown the power about the plc and reconnect it again i want to execute some of instruction only one time (as make a homing for the servo motor in the begining of starting ).
what should i use from ob to achieve my aim?

best regards

MAHER

What type of PLC are you using? If it's an S7 300/400 you can add OB100 to the program. It will be executed once at startup; so enter all initializing routines in OB100.

hi sir
the type of the plc is s7 315-2dp, i will try to use this ob100
but , can i use plcsim to check this ob100 ( the instruction which on ob100 can i test it by using plcsim or not ?)

thanks for fast replying
best regards

maher