Re: Whats the simplest way to do the following (digital design) ...

On Jul 7, 5:50 am, Fred Bloggs <nos...@xxxxxxxxxx> wrote:
I have a system which have three (output) monitor signals. If the system
runs as normal, the three signals are zero. If there is a fault, one (or
more) of the monitoring signals will become one. Also, the system has a
shutdown intput. Put a zero here, and the system runs; put a one here
and the system stops.

Now, to the problem: I want to build a device (e.g. with 74... ICs) with
three inputs, one output and three LEDs. The three inputs connects to
the monitor signals, and the output connects to the shutdown output.
When one (or more) of the inputs becomes one (indicating an error), the
output should become one (to shut the system down). The three LEDs
should indicate witch of the input(s) that caused the shutdown.

Note, when the system shuts down, the montoring signals may, or may not
reset to zero.

Whats the simplest way to do this (least amount of ICs) ?

Best Regards Johan.

Latch the occurrence of the fault signals- that would be a combinatorial
S-R latch.


The OP didn't say whether the reset input needs to be held true until
the fault signal is cleared or whether there is a manual clear input
or what. A lot is left unstated.

This sounds a lot like a homework problem. The question is really
asking for a circuit the performs a certain function and dresses it up
with needless details.


BTW: For the OP. Lighting a LED is best done by putting a resistor
and the LED in series and hooking it to the Vcc and pulling the other
end down with a gate. TTL and HCT parts pull down better than up.


.

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