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| title | aliases | tags | |
|---|---|---|---|
| sequential-circuits |
|
combinatorial-logic-circuits always produce the same outputs given the same input. Sequential curcuits on the other hand, produce different outputs depending on past history and the inputs.
There are two main types of sequential circuit
- Sychronous
- this is when changes of state occur in time with a clock cycle
- changes of input occur between clock pulses
- state changes occur at the clock pulses
- Asynchronous
- state changes occur as the inputs occur
- event driven
Main circuits
SR latch
The set reset latch is the most basic and simple sequential circuit. It is anychronous
The ouput is remembered and changed basic on previous output.
- When S (set) is pulsed Q is one and Q̄ is zero
- When R (reset) is pulsed Q is set to zero and Q̄ is set to one
D Flip FLop
The D flip flop is basically an SR connected to a clock. Making it synchronous.
Instead of switching when you set or reset. The outputs change when the clock pulses. Depending on the value of the D(ata) input.
T Flip Flop
The T flip flop swtiches between the two outputs Q and Q̄ when
- T(oggle) is held high
- And the clock is cycled (from off to on to off)
JK Flip Flop
The JK flip flop is a combination of the d flip flop and the t flip flop.
| J | K | Result |
|---|---|---|
| 0 | 0 | No Change |
| 0 | 1 | Set |
| 1 | 0 | Reset |
| 1 | 1 | Toggle |
It can be used as a toggle and as a d flip flop.
Synchronous Counter
