Hi Ashok Naphade,

In contrast to the S7-300 the S7-1500 supports more organization blocks of the same type. With block numbers starting from 123 the type of the organization block is not recognizable by its number.

The use of more cyclic program OBs is helpful to modualize your program. If you are building a machine that allows some optional parts, you can put all the option-related code in a separate OB and then easily remove this part when you deliver the machine without the option.

Kind regards
Stefan