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I've built a JK flipflop - specifically, the A version, from Redstone JK flip-flops - and it works - sort of. It doesn't behave as described in the wiki, and I'm not sure if the wiki description is wrong, or if I built something wrong - or maybe the Beta release changed something.

The wiki says that the type-A flip-flop is edge-triggered, and will change its output when the Clock goes from 0 to 1, or 1 to 0. For a Clock, I'm using a Switch on the side of a block (with three Redstone wires between it and the circuit, rather than the one wire in the diagram - for some reason, it breaks with only one wire between two blocks.)

When I flip the switch down, it transitions from 0 to 1 (unpowered to powered wire), which causes the Output to change, as expected. But when I flip the switch back up (transition from 1 to 0), I get no Output change (for any combination of J and K).

Just for fun, I hooked up a 5-Clock as input, in case there was something strange about switches on blocks. But again, the Output only changed when the wire from the Clock went from unpowered to powered, and not the other way.

So is that how a JK flip-flop really works? At least in Minecraft, not the real world. :)

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  • For the real world, try electronics.stackexchange.com. That actually might be a good place for this question even with the Minecraft references.
    – mmyers
    Commented Mar 18, 2011 at 20:38
  • Yes, typically a flip-flop will only change on a certain kind of edge (either low-to-high or high-to-low). It sounds like your FF is only triggering on a rising edge, which is typical behavior.
    – Sapph
    Commented Mar 18, 2011 at 21:24
  • @mmyers, that's assuming Minecraft redstone replicates real-world electronics with sufficiently high accuracy. I'm not sure that self-lighting torches that flash and can burn out and relight, meet that standard. :) (Granted, it does seem to, for this question).
    – Cyclops
    Commented Mar 19, 2011 at 1:13
  • 1
    @Cyclops, these logic gates behave as their names suggest.
    – mrr
    Commented Jun 25, 2012 at 7:54

3 Answers 3

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Wiki kinda made a mistake: by the "C changes from 0 to 1 or 1 to 0" it means you can design it to be edge up trigger or edge down trigger not both. If you look at the design it self you will see that the first split from input C only send pulse transitions when you change it from 0 to 1 and when you change it from 1 to 0 it's doing nothing. So this work's alright just a little miss understanding, if you need so here the edge down design I built(just added not before the C):

JKFF edge down design

I fixed this in wiki so this should be fine now.

Btw you can design both edge up and down trigger, you need to send pulse(circled in black) each time the clock is changing. Do it your self as a challenge ☺

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  • Very nice change to the wiki - the most concise edit possible that actually works - adding an 'x' to change or to xor. :)
    – Cyclops
    Commented Mar 19, 2011 at 1:17
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Flip flops are either positive edge triggered or negative edge triggered but not both =)

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  • Actually, that's already been answered, thanks anyway.
    – Cyclops
    Commented Mar 20, 2011 at 1:12
  • Sorry about that. Commented Apr 26, 2011 at 21:07
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Best Vertical JK Flip-flop:

http://postimg.org/image/hnaq9jwpf/

Blue = Input (J, K)

Yellow = Clock

Red = Output (Q, /Q)

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  • That's really hot
    – minseong
    Commented Oct 1, 2017 at 10:34

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