Which is essentially what UL 1998 requires for the product design. I agree with keeping software/programmable devices out of the safety business as much as possible so you can skip the significant engineering investment required to do it properly.
-Dave From: Carl Newton [mailto:[email protected]] Sent: Thursday, August 04, 2016 10:54 AM To: [email protected] Subject: Re: [PSES] SAFETTY FEATURES controlled by ....SOFTWARE My experience with UL Medical (as an example) is that their position is that software fails 100% of the time from a safety point of view (and I agree with that view). The manufacturer would have to prove to the lab that it is fail-safe, which is probably not a desirable task on the part of the designers, and may not be possible from a practical point of view. I've been told that in those unusual cases where software/firmware has been allowed as protection against hazards is when the software/firmware is completely separated from any other system software (standalone) within the hardware architecture so that it cannot be corrupted and will have only that one dedicated function. Carl On 8/3/2016 10:32 AM, Bolintineanu, Constantin wrote: Dear Colleagues, I would like to kindly ask those who have an extensive experience regarding the above subject, to share their opinion about the following aspect: Having a circuit which is charging a battery, and having it controlled and protected by SOFTWARE ONLY from the point of view of CHARGING , DISCHARGING, OVERCHARGING, 1. How do you think that SINGLE FAULT CONDITIONS shall be applied? (without SOFTWARE working at all? Or by providing a fault on the component where the SOFTWARE is stored? OR BOTH 2. Which conditions do you think that shall be imposed to the software and/or to the memory in which it is stored? Any other suggestions/observations/comments are more than welcome. Sincerely, Constantin Bolintineanu P.Eng. ________________________________ This e-mail contains privileged and confidential information intended for the use of the addressees named above. 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