Optimization considerations

The SIDirect Communication Driver uses the following same optimization considerations as the S7 Communication Driver:

• Use different Poke modes.

• Use different reading optimization modes.

• Use cyclic services to minimize traffic.

• Use block services to minimize traffic.

The Communication Driver can also optimize its performance in getting data from the PLC by using the optimization mode. The following options are available:

• S7 SAPI
  The S7 SAPI mode is the same optimization mode used in the pre-release of the former Wonderware Siemens SIMATIC NET S7 I/O Server. This mode is implemented to keep the server compatible to the former server. This mode is the less-preferred optimization mode.

• Block Read
  The Block Read mode always registers a whole byte array containing some items. If you frequently switch items (activating and deactivating) that have similar addresses, this mode is the best selection. In this mode, there are less activations and deactivations on the protocol.

• Auto
  By default, the Auto mode is best to use when exploiting the whole PDU (Protocol Data Unit). The Auto mode has the best performance in cases where you do not make many activations and deactivations. The S7-300 family of controllers can process PDU lengths of 480 to 960 bytes, depending on the controller. An S7-400 controller can process PDU lengths of 960 bytes.

  Note: The S7-1200 and 1500 PLCs do not support cyclic services or SAPI.