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Connectivity in Control Systems Slide 17

Shown on this slide is an example of an application of IEEE-1588. Before IEEE-1588 was developed, Ethernet communication was absolute determinism. In this example the sender or host sends a control instruction to turn to a controller, and it is assumed that the sender clock, clock S, and the receiver or controller clock, clock C, are not synchronized. The sender asks the controller to turn upon receipt of the instruction; there is no telling when the controller will actually receive the command turn on, so maybe a couple milliseconds, maybe a few microseconds, maybe a few seconds, or maybe a few minutes later the controller actually turns. In the second example, the sender asks the controller to turn on at a given time, or alpha. Because the clocks are not linked or synchronized clocks, there is still a problem with the command. The sender alpha and controller alpha are not synched and the turn may happen at a random time. The bottom example shows the same command, with IEEE-1588. The clocks are synchronized to a master and there is now determinism in the system. When the sender asks the controller to turn on at alpha the controller turns at alpha and is ready for the next command.

PTM Published on: 2012-12-27