[AR] Re: LEO radiation shielding
- From: Uwe Klein <uwe@xxxxxxxxxxxxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Sat, 21 Dec 2019 10:38:41 +0100
Am 21.12.2019 um 09:15 schrieb Henry Spencer:
What nobody had noticed, until the postmortem after the failure, was
that the misbehavior was always in the first test of the day, after the
hardware had been powered down overnight. Internal nodes inside FPGAs
can hold charge for a surprisingly long time after the power has been
turned off, and this can make a difference in how the system powers up
again, especially if the designer hasn't paid enough attention to
forcing clean reset on power-up. When they did *long* power-downs, the
problem was reproducible.
It is essential that you have a reliable "power good" mechanism
and that it works in both directions
Power Up AND Power Down and that it is not dependent on any min
rise/fall times ( aka Brown Out protection )
Next step is creating a known start condition.
it can be a good idea to have a nonvolatile reset counter.
And you don't connect pyros directly to FPGA outputs.
Add some Interlock or other mechanism should be in between.
like sequential action to trigger a pyro device.
Uwe
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