PPRuNe Forums - View Single Post - Boeing 787s must be turned off and on every 51 days
Old 7th Apr 2020, 05:49
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Check Airman
 
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Originally Posted by DaveReidUK
Counters, and microprocessor registers in general, typically have a capacity that corresponds to some multiple of 8 bits.

For example a 16-bit counter isn't capable of counting beyond 65,535 (one less than 2^16). Using one for an application that requires counting to values higher than that will produce unpredictable results.

In the case of the 787 issue, whatever the maximum value that the counter can accommodate is (2^32 is being suggested, equivalent to 4,294,967,295 clock ticks), that value is reached after approximately 51 days.
Appreciate the explanation. Am I to assume that there's some sort of clock somewhere on the plane that was only designed to count up to 2^32, and so will need to be reset before it gets to that value, so it doesn't run out of fingers to count on?
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