Specify this S-function should be placed as soon as possible
Specifies that this S-function should be placed as soon as possible in the block sorted order. The SS_OPTION_PLACE_ASAP option uses a hierarchical sorted order such as that used by blocks (Rules for Block Priorities). Within a subsystem, the Simulink® engine places an S-function block using this option as far up in the sorted order as possible without changing the model's semantics. If the S-function's Priority block property is set, and other blocks in the same subsystem have the same priority, the engine places S-functions with this option before the other blocks in the same subsystem with the same priority. This option is typically used by devices connecting to hardware when you want to ensure the hardware connection is completed first.
Note: Simulink honors the SS_OPTION_PLACE_ASAP option, relative to other blocks, only if this block and the other blocks are in the same subsystem. As a result, Simulink does not compare two blocks set with SS_OPTION_PLACE_ASAP if they exist in different subsystems. In addition, Simulink might not place blocks with SS_OPTION_PLACE_ASAP set before blocks without SS_OPTION_PLACE_ASAP set if they are in different subsystems.
For more information on block sorted orders, see What Is Sorted Order?.