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Re: Re:"hard reset"



A hard reset usually does all the initialization that is required at power
up so it would generally assume that the data in RAM is random. I wasn't one
of the designers of AO-40 so I am only speculating based on other designs
that I have seen and the fact that the controllers want to avoid a hard
reset.

John
KD6OZH

----- Original Message -----
From: "Bruce Bostwick" <lihan@ccwf.cc.utexas.edu>
To: <amsat-bb@AMSAT.Org>
Sent: Tuesday, 19 December 2000 13:06 UTC
Subject: Re: [amsat-bb] Re:"hard reset"


> >On Mon, Dec 18, 2000 at 08:13:16PM -0000, John Stephensen, KD6OZH wrote:
> >> The AO-40 IHU most likely works like others that I have seen. A "hard
reset"
> >> will reset the CPU and all peripherals and reboot the system. The AO-40
IHU
> >> has error-correcting memory so one of the first things that must be
done
> >> after reset is to write zeros into memory. This is because the memory
will
> >> start up full of random bits and half of the bit combinations are
guaranteed
> >> to activate the error correction hardware and interrupt the CPU
> >
> >IMO, the memory would only return to random bits if the devices
> >were actually powered down and up again. At least in the case of
> >static RAM, anyway (which in my experience does not typically
> >have a reset signal). I suppose this could occur if the controller
> >for dynamic memory missed a few refresh cycles during a reset though.
> >Does AO40's IHU-1 use DRAM?
>
> According to the P3D site, if my aging memory serves, the IHU's use
> radiation-hard processors and rad-hard CMOS static RAM, which does require
> power to retain contents but does not require refresh.  As long as the
SRAM
> has power, it will retain its data .. in my experience SRAM will hold its
> data without power for a surprisingly long time as well, although with
> progressively more bit errors with longer power dropouts ..
>
>
> <BGB>
>                  --... ...--  -.. .  -. ..... ...- -...
>              Bruce Bostwick  N5VB  Austin, TX  Grid EM10DH
>     ARRL / UT ARC / Austin ARC / Travis Co. ARES / W5YI Vol. Examiner
>    http://ccwf.cc.utexas.edu/~lihan/  mailto:lihan@ccwf.cc.utexas.edu
>
>
>
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