Despite claiming real-time support, many embedded systems only have a passing relationship with the clock. That is beginning to change as designers try to build safer systems. ALMOST 11 YEARS ago the electrical network in the north-east of the USA blacked out for hours as problems with distribution equipment rippled through the network. As investigators pored over the data that might lead to its cause, they ran quickly into one major problem: none of the data gave easy clues as to when it was recorded. The report claimed: "The Task Force's investigators laboured over thousands of data items to determine the sequence of events, much like putting together small pieces of a very large puzzle. That process would have been significantly faster and easier if there had been wider use of synchronised data-recording devices." The following February, the US National Electric Reliability Council issued the recommendation that the data-acquisition devices inside power plants and substations should be time-synchronised so that the data they record could easily be assembled on a consistent timeline. The move represents part of a trend to stop time from being the forgotten component in embedded systems as they start to link up together as components of the Internet of Things (IoT). Because many of these systems will involve some level of motor or robotic control - a class of computerised mechanisms known as cyber-physical systems - safety plays a major role in the decision to look much more closely at timing.
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