Description 

CALL <logic block identifier> is used to call functions (FCs) or function blocks (FBs), system functions (SFCs) or system function blocks (SFBs) or to call the standard pre-programmed blocks shipped by Siemens. The CALL instruction calls the FC and SFC or the FB and SFB that you input as an address, independent of the RLO or any other condition. If you call an FB or SFB with CALL, you must provide the block with an associated instance DB. The calling block program continues logic processing after the called block is processed. The address for the logic block can be specified absolutely or symbolically. Register contents are restored after an SFB/SFC call.

英文解释是这样的