What Is a Flip-Flop?
A flip-flop is the most basic digital memory element that can store a single bit (0 or 1). Unlike logic gates, it "remembers" its state; so it's the basis of sequential circuits.
How Does It Work?
It's made of logic gates that feed each other and has two stable states (0 or 1). When triggered by a clock signal, it takes the value at its input and holds it until the next trigger.
Difference From a Logic Gate
A gate only looks at the instantaneous input (combinational); a flip-flop stores the past state (sequential). This "memory" property is needed for counting, storing and state machines.
| Type | Property |
|---|---|
| D (Data) | Copies the input at the clock edge |
| JK | Flexible; set/reset/toggle |
| T (Toggle) | Flips the state on every clock |
Clock and Edge Triggering
Most flip-flops trigger on the rising or falling edge of the clock. The higher the frequency, the faster the circuit works; if setup/hold times are violated the data is corrupted.
Where Is It Used?
Counters, shift registers, state machines, synchronization and register/memory cells.
Common Mistakes
- Setup/hold violation: if data changes too close to the clock edge, metastability occurs.
- Asynchronous input: using external signals without synchronizing them causes instability.
- Forgetting reset: a reset is needed to avoid an unknown state at startup.
Frequently Asked Questions
What's the difference between a flip-flop and a latch?+
How many bits does it store?+
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