Flip & flop by Zaheer Abbas Aghani

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  • 1. 1..FLIP & FLOPA traditional flip-flop circuit based on bipolar junction transistorsIn electronics, a flip-flop is a circuit that has two stable states and can be used to storestate information. The circuit can be made to change state by signals applied to one ormore control inputs and will have one or two outputs. A circuit incorporating flip-flopshas the attribute of state; its output depends not only on its current input, but also on itsprevious inputs. Such a circuit is described as sequential logic. Where a single input isprovided, the circuit changes state every time a pulse appears on the input signal. Sincethe flip-flop retains the state after the signal pulses are removed, one type of flip-flopcircuit is also called a "latch". Other types of flip-flops may have inputs that set aparticular state, set the opposite state, or change states, depending on which input ispulsed.Flip-flops are used as data storage elements, for counting of pulses, and for synchronizingrandomly-timed input signals to some reference timing signal. Flip-flops are afundamental building block of digital electronics systems used in computers,communications, and many other types of systems.Read more: http://www.answers.com/topic/flip-flop-electronics#ixzz1HWhF4dmG

2. TYPES OF FLIP & FLOPD flip-flopD flip-flop symbolThe D ip-op is the most common flip-flop in use today. It is better known as data ordelay flip-flop (as its output Q looks like a delay of input D).The Q output takes on the state of the D input at the moment of a positive edge at theclock pin (or negative edge if the clock input is active low).[23] It is called the D flip-flopfor this reason, since the output takes the value of the D input or data input, and delays itby one clock cycle. The D flip-flop can be interpreted as a primitive memory cell, zero-order hold, or delay line. Whenever the clock pulses, the value of Qnext is D and Qprevotherwise.Truth table: Clock D Q Qprev Rising edge 0 0 X 3. Rising edge 1 1X Non-Rising X QprevT FLIP AND FLOPT flip-flopA circuit symbol for a T-type flip-flopIf the T input is high, the T flip-flop changes state ("toggles") whenever the clock input isstrobed. If the T input is low, the flip-flop holds the previous value. This behavior isdescribed by the characteristic equation: (expanding the XOR operator)and can be described in a truth table: T flip-flop operation[25] Characteristic table Excitation tableT Q Qnext CommentQ Qnext T Comment0 0 0 hold state (no clk) 0 0 0 No change0 1 1 hold state (no clk) 1 1 0 No change1 0 1toggle 0 1 1 Complement1 1 0toggle 1 0 1 ComplementWhen T is held high, the toggle flip-flop divides the clock frequency by two; that is, ifclock frequency is 4 MHz, the output frequency obtained from the flip-flop will be 4. 2 MHz. This "divide by" feature has application in various types of digital counters. A Tflip-flop can also be built using a JK flip-flop (J & K pins are connected together and actas T) or D flip-flop (T input and Qprevious is connected to the D input through an XORgate). A T flip-flop can also be built using an edge-triggered D flip-flop with its D inputfed from its own inverted output.JK FLIP & FLOPJK flip-flopA circuit symbol for a positive-edge-triggered JK flip-flopJK flip-flop timing diagramThe JK flip-flop augments the behavior of the SR flip-flop (J=Set, K=Reset) byinterpreting the S = R = 1 condition as a "flip" or toggle command. Specifically, thecombination J = 1, K = 0 is a command to set the flip-flop; the combination J = 0, K = 1is a command to reset the flip-flop; and the combination J = K = 1 is a command totoggle the flip-flop, i.e., change its output to the logical complement of its current value.Setting J = K = 0 does NOT result in a D flip-flop, but rather, will hold the current state.To synthesize a D flip-flop, simply set K equal to the complement of J. The JK flip-flopis therefore a universal flip-flop, because it can be configured to work as an SR flip-flop,a D flip-flop, or a T flip-flop.NOTE: The flip-flop is positive-edge triggered (rising clock pulse) as seen in the timingdiagram.The characteristic equation of the JK flip-flop is: 5. and the corresponding truth table is: JK Flip Flop operation[25]Characteristic table Excitation tableJ K Qnext Comment Q Qnext J K Comment0 0 Q hold state 0 0 0 X No change0 1 0 reset0 1 1X Set1 0 1set 1 0 X 1 Reset1 1 Qtoggle 1 1 X 0 No changeRs flip and flop) SR flip-flop - (Or "RS flip-flop") A "set/reset" flip-flop in which activating the "S" input will switchit to one stable state and activating the "R" input will switch it to the other state. The outputs of a basic SR flip-flop change whenever its R or S inputs change appropriately. A clocked SR flip-flop has an extra clock input which enables or disables the other two inputs. When they are disabled the outputs remain constant. If we connect two clocked SR flip-flops so that the Q and /Q outputs of the first, "master" flip-flop drive the S and R inputs of the second, "slave" flip-flop, and we drive the slaves clock input with an inverted version of the masters clock, then we have an edge-triggered RS flip-flop. The external R and S inputs of this device are latched on one edge (transition) of the clock (e.g. the falling edge) and the outputs will only change on the next opposite (rising) edge. If both R and S inputs are active (when enabled), a race condition occurs and the outputs will be in an indeterminate state. A JK flip-flop avoids this possibility.2..Counter In digital logic and computing, a counter is a device which stores(and sometimes displays) the number of times a particular event or process has occurred,often in relationship to a clock signal 6. Types.Up/down counterA counter that can change state in either direction, under the control of an up/downselector input, is known as an up/down counter. When the selector is in the up state, thecounter increments its value. When the selector is in the down state, the counterdecrements the count.4..Digital logic designCombinational And Sequential Circuit Analysis And Design, Digital Circuit Design OptimizationMethods Using Random Logic Gates, Multiplexers, Decoders, Registers, Counters, AndProgrammable Logic Arrays. Computer Aided Tools In The Design, Simulation, And Testing OfDigital Circuits.Importance of digital logic designNew, due to popular request! I have received a number of questions regarding the internal structure and operation of logic gates. This is not as simple as it may seem, because there are many different ways to implement logical functions electronically. Therefore, I am now adding some new pages on the major logic families and their internal operation.Ive also had some requests regarding building and demonstrating actual circuits to perform logical functions. If youd like to get some hands-on experience, Ive set up a series of pages on breadboarding logic circuits to demonstrate their operation. If these prove as popular as I expect, I will add to the list soon. 7. Digital or binary logic has fascinated many people over the years. The very idea that a two-valued number system can possibly be the basis for the most powerful and sophisticated computers seems astounding, to say the least. Nevertheless, it is so, and the how and the why of this requires some explanation.Everything in the digital world is based on the binary number system. Numerically, this involves only two symbols: 0 and 1. Logically, we can use these symbols or we can equate them with others according to the needs of the moment. Thus, when dealing with digital logic, we can specify that:0 = false = no1 = true = yes Using this two-valued logic system, every statement or condition must be either "true" or "false;" it cannot be partly true and partly false. While this approach may seem limited, it actually works quite nicely, and can be expanded to express very complex relationships and interactions among any number of individual conditions. One essential reason for basing logical operations on the binary number system is that it is easy to design simple, stable electronic circuits that can switch back and forth between two clearly-defined states, with no ambiguity attached. It is also readily possible to design and build circuits that will remain indefinitely in one state unless and until they are deliberately switched to the other state. This makes it possible to construct a machine (the computer) which can remember sequences of events and adjust its behavior accordingly.ApplicationsDigital electronicsFrom Wikipedia, the free encyclopediaJump to: navigation, searchDigital electronics represent signals by discrete bands of analog levels, rather than by acontinuous range. All levels within a band represent the same signal state. Relativelysmall changes to the analog signal levels due to manufacturing tolerance, signalattenuation or parasitic noise do not leave the discrete envelope, and as a result areignored by signal state sensing circuitry. 8. In most cases the number of these states is two, and they are represented by two voltagebands: one near a reference value (typically termed as "ground" or zero volts) and a valuenear the supply voltage, corresponding to the "false" ("0") and "true" ("1") values of theboolean domain respectively. An industrial digital controller Intel 80486DX2 microprocessorDigital techniques are useful because it is easier to get an electronic device to switch intoone of a number of known states than to accurately reproduce a continuous range ofvalues.Digital electronic circuits are usually made from large assemblies of logic gates, simpleelectronic representations of Boolean logic functions.[1]AdvantagesOne advantage of digital circuits when compared to analog circuits is [2] that signalsrepresented digitally can be transmitted without degradation due to noise. For example, acontinuous audio signal, transmitted as a sequence of 1s and 0s, can be reconstruc