The fastest network in the world won’t give you deterministic performance unless the software that is sending the messages is structured for real-time results. Fortunately, soft-logic programs, HMI software and most similar applications use deterministic I/O polling and utilize real-time task scheduling techniques.

The basic scheme used by I/O drivers in industrial software is to poll I/O in a deterministic fixed sequence, (much like the classic PLC scheme) to insure repeatable and "determined" results. This fixed polling guarantees that collisions will not occur if you use a Dedicated Control Network. If there is only one master on the network (typically your logic or HMI software in the central network node) and it polls its I/O in an effective manner, real-time results can be achieved.

Beyond this, there are ways to get faster real-time results than classic determinism. By intelligently polling I/O (only asking for I/O that is needed during each operation), better efficiency and performance can result. The classic name for this technique is "Report by Exception".

SIXNET I/O updating software uses another technique that is even more efficient. With detailed knowledge of the capabilities of an Ethernet network, SIXNET software polls multiple stations simultaneously by putting multiple messages into the Ethernet buffer and keeping track of the responses with real-time scheduling algorithms. These techniques speed up I/O polling in the SIXNET Control Room Windows software (the IOmap Shared Resource Database used by many high-end SCADA packages) and in the peer-to-peer I/O moves configured into SIXNET gateways. In effect, SIXNET systems multiply network speed.