---------------------------------------
    Whoops, accidentally hit SEND too soon.
    ---------------------------------------

Brendan Moran <PICLIST@mitvma.mit.edu> wrote:

> Determine the time it takes for the processor to be garaunteed to
> have all its volatile RAM fail.  Program a one-shot to that length
> of time.  Attach an edge triggered one-shot to the processor's
> power pins.  Then, have the processor trigger the one-shot, which
> will force it to power down, and stay off until all its RAM is
> gone.

    Brendan:

    The time for RAM to fail -- to "forget" its contents -- can be
    VERY long:  Many seconds at room temperature, and much longer at
    low temperatures.

    Also... RAM "failure" isn't the same as RAM "clear".  RAMs
    generally power-up in an arbitrary state, so even removing power
    for a year won't ensure that the RAM would be clear on power-up.

> I admit it's a little short of trap doors, and before you sneer at
> me, consider the possibilities a bit.

    No sneering here.  I hope you didn't take offense at my earlier
    comment; none was intended.

> If it takes less time for this than the large volume of instruction
> cycles to clear all the RAM, then it should be worth it, right?

    Well, no, not necessarily.  Length of time from power application
    to all RAM clear is rarely a critical factor in a circuit design.


    -Andy

=== Andrew Warren -- aiw@cypress.com
=== Principal Design Engineer
=== Cypress Semiconductor Corporation
===
=== Opinions expressed above do not
=== necessarily represent those of
=== Cypress Semiconductor Corporation

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads