In electronics there are two values 0 and 1, so in edge triggered flip-flops what is the value of voltage at the edge, is it 1 or 0?

  • \$\begingroup\$ Depends 0 or 1 are meaningless unless you assign a meaning to them like voltage, typically 1 or True is assigned to a high voltage level \$\endgroup\$ – Voltage Spike Nov 13 '17 at 4:21

It is neither 0 nor 1. An edge means a transition from 0 to 1 (positive-going edge) or from 1 to 0 (negative-going edge).

An edge-triggered flip-flop is a device which performs its task only when the clock input detects an edge. That is, only in the instant when the edge is detected the FF does its job.

Terminology note: usually you'll see shorthand terms like "positive edge" and "negative edge". They mean the same as "positive-going edge" (a.k.a. rising edge) and "negative-going edge" (a.k.a. falling edge).

To be more specific, since I explained the thing in a very simplified way, you should be aware that the other inputs of the FF must meet some timing requirements relative to the clock edge in order for the FF to behave correctly.

In particular, the inputs must be stable for a minimum time before the clock edge (that's called the setup time) and must remain stable for a minimum time after that edge (that's called the hold time, which can sometimes be zero, for specific technologies).

If you don't meet those requirements your FF (or any other synchronous sequential digital network, which is the category to which the edge-triggered FF belongs) may (and usually will) do funny things (read: it could misbehave).

  • \$\begingroup\$ +1, however it is important to note that while in that transition odd things can happen if the other inputs change within the rise or fall time of the clock. As such the clock edge needs to be short and, if you can, the data needs to be synchronous. \$\endgroup\$ – Trevor_G Nov 12 '17 at 17:30
  • \$\begingroup\$ Excellent; perhaps showing the range of input voltages where the input actually clocks may be informative. \$\endgroup\$ – Peter Smith Nov 12 '17 at 18:05
  • \$\begingroup\$ I am asking what's in between the transition? \$\endgroup\$ – ashwini abhishek Nov 12 '17 at 18:44
  • \$\begingroup\$ How does it know that it's transitioning? \$\endgroup\$ – ashwini abhishek Nov 12 '17 at 18:45
  • \$\begingroup\$ @PeterSmith Thanks! No time to expand on this right now. Feel free to add your answer to complement mine! \$\endgroup\$ – Lorenzo Donati supports Monica Nov 12 '17 at 19:18

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