24 hour countdown timer with 1 hour warning

Thread Starter

badboydano

Joined Mar 4, 2011
2
I'm using a MX073 as a 24 hour count down timer.
When there is 1 hour left, I want a warning signal to commence.
At 59 minutes 59 seconds, digit 6 is blank and digit 5 is a zero.
I have a logic cct that goes high when digit 6 is blank.
I have a logic cct that goes high when digit 5 is a zero.
Now I need a logic cct that goes high when both conditions are true.
I think that the problem I face is this:
These conditions do not exist at the same time.
I think that digit 6 turns on then off and then digit 5 turns on then off.
I think that I have to find a way of "slowing" digit 6 down so that it happens the same time as digit 5.
I have attached cct diagrams to help explain.
I think that I can use an RC cct to slow (delay) it.
But I don't know how long to delay it for.
I think that it is maybe 1 clock cycle.
Question:
Does anyone know how long a clock cycle might be in an ATMEG8?
I don't have access to an ohh-silly-scope.
I don't know if it is using it's own internal clock cycle or "borrowing"
one from it's DS1307 buddy.
Any thoughts, anyone?
Thanks, Badboydano
 

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