At 03:47 PM 8/20/02 -0700, you wrote:
>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.

Fail? Do you mean here to have all ram go "clear"?

If so, you will find that you must wait forever. You have no guarantee that
the ram will be "clear" (zero, or whatever) at power up.

You don't know what ram will be at power up.  This is exactly why people
who care write routines to clear ram at the beginning of their programs. Or
set it to some other known state.

A colleague once demonstrated to me how easy it was to write a quick 10
step program and load it into an 1802 processor via a terminal program.
The target system had a solenoid and his program made it click on/off at
about a 1Hz rate.  Thinking to clear it from memory, he turned the power
off for a couple of seconds and back on. The solenoid began to click again.
The memory had not cleared.

A voltmeter revealed that the ram power had indeed dropped to below .5
volts but it did not forget.  We tested some more and found that the power
could be off for over 45 seconds before the program would not run at power
up, ie, it had scrambled at least one ram location needed for the program.

Tom M.

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