Re: "RESET"

On 5/24/2025 5:37 PM, Carlos E. R. wrote:

Even the initial microprocessors have a reset pin. When they are powered up, the status of the electronics is unknown, so a small time after power up, the line is triggered by a timer (555 or whatever).

Usually, reset is asserted as power is being applied (PoR).  One can
also design silicon with internal reset generators (though these often
rely on particular power application characteristics)
But, thereafter, there should be no need to be able to FORCE a reset
condition beyond that which occurs as part of PoR.
It certainly shouldn't be needed to recover from an errant processor.

Then, there are many designs where you can not pull power, because there is an unreachable battery.

So, the battery is inaccessible but a reset button wouldn't be?
All the more reason NOT to need a reset button!

Then, it is impossible to guarantee that the device will never find itself in a pickle. No matter how fantastic the designers are.

Barring hardware failures, software should be able to sort itself out,
even if it means resorting to panic() -- which can be the equivalent of
the startup code being re-executed.
For device in question (a PLC modem) likely relies on reset for
hardware design deficiencies as the software itself is pretty trivial.
It would be amusing to apply odd "DC" power to various devices and watch
how they misbehave ("Well, that's not what we expected when we specified
X volts @ Y amps"  "Oh, well asking to examine drive 7 isn't what
was expected when we designed this TWO drive machine!  Yet, if you try
to do so, you expect the software to 'behave' despite your ignorance
if what was expected?")