Re: Startup code



Paul Keinanen wrote:
> On Wed, 29 Jun 2005 21:23:56 -0500, Jack Klein <jackklein@xxxxxxxxxxx>
> wrote:
>
> >How do you do a complete memory test before calling the C start-up
> >code that requires at least some memory be working? How do you test
> >the watchdog chip by forcing a reset?
> >
> >Don't any of you do serious POST testing of your hardware?
>
> While all kinds of self tests are nice, but the real question is what
> to do, if the test fails.
>
> For a critical redundant control system, the only thing would be to
> take the device off-line and let the redundant system(s) take over and
> let them raise the alarm. For other systems, in which faulty data can
> be harmful, some means of checking the device integrity is needed.

For a safety device we made we had self tests for 30 seconds
after reset and continuously by slices during the normal
operation. If either test fail, the application is stopped
immediately and the system must be designed so that all
outputs are put in a safe state in this case. This is a
regulatory issue. A safety device must have a safe state
in the absence of voltage. This is also an issue for the
whole installation, not only the equipment.

Every hardware component is tested, including outputs by
feedback to inputs and inputs by alternating input voltage
instead of continuous voltage.

> For a harmless toy (and "toy" is here used in a broader sense), if the
> POST detects a problem, what could the user do, especially if there is
> no display. So realistically, why test something, if there are no
> actions to be taken to rectify the problem other than throwing the
> malfunctioning device away ?
>
> Paul

.

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