Re: How does DO-178 treat OEM modules (with software)?

On Mar 29, 12:37 pm, "Thomas Magma" <somewh...@xxxxxxxxxxxxxxxxxx>
wrote:
A while back we had a short seminar on DO-178 and I asked the 'experts' how
DO-178 dealt with the software in modules from a third party (I used GPS as
an example). They said that as long as our software treated the GPS module
as a black box or a slave, that we didn't have to ensure that the GPS
module's software was DO-178. Is this true or still true? What about modules
in general? I have the standard but can't find the answer anywhere in it.

Thomas Magma

It can go either way, there is no doubt that there is DO-178 Level A
certified SW out there that contains modules that have untested (in
the formal sense) software/firmware. These modules can be separate HW
modules or preprogrammed chips within the Level A HW itself.

Effectively you are looking at the module like a black box as the
"experts" claimed, whether it has software it it, or firmware, or PLD
code or logic gates to implement the task, is irrelevant.

There are a few key elements, one is that is it a slave to the Level A
SW? In that if it failed the Level A SW could handle the failure,
either by selecting an alternate input (another GPS module) or use a
secondary input.

The second is could the slave take down the Level A SW (say by
continuously toggling an interrupt to the Level A HW). You have to
assume normal failure modes in this case. Additionally you have to
think about if some software programmer intentionally wanted to
corrupt/take down the Level A HW, could he do it? If the answer is yes
then that module has to be Level A.

The dumber and fewer interconnects between the module and the Level A
SW the better.


.

Relevant Pages

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