Rangkaian Sekuensial Rangkaian Sekuensial Flip-flop
Combinational versus Sequential Functions Logic functions are categorized as being either combinational (sometimes referred to as combinatorial) or sequential. In the case of a combinational function, the logic values on that function s outputs are directly related to the current combination of values on its inputs. In the case of a sequential function, the logic values on that function s outputs depend not only on its current input values, but also on previous input values.
Sequential Functions That is, the output values depend on a sequence of input values. Because sequential functions remember previous input values, they are also referred to as memory elements.
RS Latches One of the simpler sequential functions is that of an RS latch, which can be implemented using two NOR gates connected in a back-to-back configuration
RS Latches The secret of the RS latch s ability to remember previous input values is based on a technique known as feedback. This refers to the feeding back of the outputs as additional inputs into the function.
RS Latches
RS Latches
RS Latches
RS latch two NAND
D-Type Latches A more sophisticated function called a D-type ( data-type ) latch can be constructed by attaching two ANDs and a NOT to the front of an RS latch
D-Type Latches
D-Type Flip-flops In the case of a D-type flip-flop (which may also be referred to as a register), the data appears to be loaded when a transition, or edge, occurs on the clock input A transition from 0 to 1 is known as a rising-edge or a positive edge, while a transition from 1 to 0 is known as a falling-edge or a negative-edge A D-type flip-flop s clock input may be positive-edge or negative-edge triggered
D-Type Flip-flops
D-Type Flip-flops Waveform
D-Type Flip-flops with Clear (Reset)
JK and T Flip-flops T flip-flop doesn t have any data inputs; the outputs simply toggle to the inverse of their previous values on each active edge of the clock input.
Flip Flop Flip-flops are synchronous bistable devices. The term synchronous means the output changes state only when the clock input is triggered. That is, changes in the output occur in synchronization with the clock. Flip-flop is a kind of multivibrator. There are three types of multivibrators: Monostable multivibrator has only one stable state. It produces a single pulse in response to a triggering input. Bistable multivibrator exhibits two stable states. It is able to retain the two SET and RESET states indefinitely. It is commonly used as a basic building block for counters, registers and memories. Astable multivibrator has no stable state at all. It is used primarily as an oscillator to generate periodic pulse waveforms for timing purposes.
Edge-Triggered Flip-flops An edge-triggered flip-flop changes states either at the positive edge (rising edge) or at the negative edge (falling edge) of the clock pulse on the control input. The three basic types are introduced here: S-R, J-K and D.
Edge-triggered S-R flip-flop As S = 1, R = 0. Flip-flop SETS on the rising clock edge
Edge-triggered J-K flip-flop The J-K flip-flop works very similar to S-R flipflop. The only difference is that this flip-flop has NO invalid state. The outputs toggle (change to the opposite state) when both J and K inputs are HIGH. The truth table is shown below.
Edge-triggered D flip-flop The operations of a D flip-flop is much more simpler. It has only one input addition to the clock.
Pulse-Triggered (Master-Slave) Flip-flops The term pulse-triggered means that data are entered into the flip-flop on the rising edge of the clock pulse, but the output does not reflect the input state until the falling edge of the clock pulse.
Data Lock-Out Flip-flops The data lock-out flip-flop is similar to the pulse-triggered (master-slave) flip-flop except it has a dynamic clock input. The dynamic clock disables (locks out) the data inputs after the rising edge of the clock pulse. Therefore, the inputs do not need to be held constant while the clock pulse is HIGH.
Applications Frequency Division
Parallel Data Storage
Counting End of slides