Archives For WDT

And not quite as simple as you think…

The testimony of Michael Barr, in the recent Oklahoma Toyota court case highlighted problems with the design of Toyota’s watchdog timer for their Camry ETCS-i  throttle control system, amongst other things, which got me thinking about the pervasive role that watchdogs play in safety critical systems. The great strength of watchdogs is of course that they provide a safety mechanism which resides outside the state machine, which gives them fundamental design independence from what’s going on inside. By their nature they’re also simple and small scale beasts, thereby satisfying the economy of mechanism principle.

Continue Reading…