Latching events

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Anonymous
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Hi Guys,

   

I have need to latch an event, I thought this would be very simple but it is putting up quite a fight! Firstly I tried to make an RS type flip flop from two NOR gates, this refused to latch at all for some reason. I am guessing the async logic is synthesized by use of sync-subcomponents? Anyhow, it really didn't want to play.

   

 So, I tried to hook up a D type flip flop and turn the clock off by means of an AND gate and the negated output of the d-type. (As attached) This seemed to work, right up to the point where I connected the D-type output to the clock input so again it looks like some kinda race condition.

   

 I need a fast acting latch, that I can reset. any ideas? It seemed such a simple bit of the circuit...

   

Rob

1 Reply
Anonymous
Not applicable

 Use preset pin on DFF block to capture wanted event and clear Q pin by setting D-input  to 0 position and clocking DFF with control register.

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