18 Nov
2002
18 Nov
'02
5:46 p.m.
Tony wrote:
<88W> ... since
it's steady, I think we can assume it's correct (at least for the moment).
OK. I'll probe around looking for a resistor connecting high end to +5V.
What I would _expect_ is the following :
...
2) A potential divider across one of the supply rails (probably the +5V
rail), with the tap to the other input. Possibly a capacitor from the tap
to ground to provide a bit of power-on delay. The idea is to take the CPU
out of the reset state when the supply rails are high enough (== when the
comparator switches over)
The orange 6192 may be that. Its job is just to make sure the
voltage-divider tap comes up slower than the voltage reference?
I'll look for another component (a black one this time) in parallel with
the 6192, to form the bottom end of the divider.
3) A high value resistor from the output back to one of
the inputs to
provide a bit of hysteresis and prevent the darn thing oscillating. May
not be essential, but it's good practice to put it in