How create address memory word or DB

Here we are using CPU 313-2DP, we are using some on/off temperature controls by simple comparision logic, .Normally what ever setpoint is given through scada , that value is stored to Memory word and logic it's work. if PLC switched off ( Due to inside plant any Mech welding job carried ) means that value should goes to Zero. Then again we need to give setpoint value. i want to know how to solve and if PLC restart means how to take automatically it initial value, (Like 60*Cellsius by default value).

In stead of storing in MW, store the data in a Datablock.

Another alternative would be to load the desired startup value into the marker word in OB100 (Startup OB).