MADISON, Wis.– As we continue to explore the Oklahoma court judgmentagainst Toyota for unintendedacceleration, EE Times readers have raisedmany astute engineering questions, rangingfrom the probabilities of bit-flipoccurrence and safety standards applied tosoftware and hardware to the safety systemarchitecture built into Toyota cars.
Meanwhile, in a number of Toyota cases(including the Oklahoma one), one naggingquestion recurs among consumers: If thereare software bugs in the system, why havemillions of Toyota owners like ourselvesnever experienced unintended acceleration?
It turns out that Jean Bookout, theplaintiff in Bookout v. Toyota case, haddriven her Toyota for several years and put9,000 miles on the odometer without aproblem — until the crash that injured herand killed a passenger.
We would like to take you through howMichael Barr, CTO and co-founder of the BarrGroup and an expert witness who testified inthe case, concluded that a random hardwareflaw — combined with a software bug that'slatent and lurking — “can get through orknock down the fail-safes that are in place”under certain driving conditions on certaindays.
Excerpt from the court transcript
EE Times is publishing a portion of thecourt transcript relevant to the ToyotaCamry's electronic control module ECM. Thefollowing Q&A was carried out betweenBarr and Benjamin E. Baker Jr., an attorneyrepresenting the plaintiffs. This excerptbegins with Barr on the witness standdescribing the ECM, which consists of twoCPUs: a V850 supplied by NEC (which laterbecame Renesas) and an ESP-B2 supplied byDenso acting as a second CPU (sometimesreferred as a monitor CPU).
A. So thisis a photograph of the ECM. And this ECM,or engine control modules, has two bigchips on it. Has a bunch of other chips,capacitors, circuit tracers that you cansee, and other things. This biggest one,the square one, is the main CPU. It is atype of a CPU or a model of CPU called aV850. That is kind of the equivalent ofcalling it a Pentium. V850 is the modelnumber of that processor. Comes from acompany, a supplier of Toyota that used tobe called NEC. It has since changed itsname.
Then there isa second rectangular chip here, and thatchip is what has been referred to byvarious witnesses as the monitor CPU, theESP-B2, and sometimes the sub-CPU.
Importantly,each of those is a processor with its ownsoftware. Then, of course, all togetherthey comprise an embedded system.
Q. So thesoftware that we're going to talk about isstored within components on this board?
A. Almostalways when I'm talking about thesoftware, I'm talking about the softwareon this main CPU, which performs thethrottle control, the combustion, monitorsthe accelerator, and all those things,cruise control. But there is alsosoftware, and I will specifically call outwhen I'm talking about this monitor CPUand its software.
Q. This isfrom a 2008 Camry?
A. Thisparticular photo is from 2008 Camry.
Q. Is the2005 generally very similar to this?
A. The chipswould be moved around a little bit, but interms of the electronics of what is there,there is a V850 processor, there is anESP-B2. From a substantial similaritypoint of view, they are very similar.
Q. Can youtell us what this is?
To read more of Michael Barr’s testimony, go to the rest of the Bookout versus Toyota Motorola transcript on EETimes.