Excitation Table Of Jk Flip Flop


What is the excitation table of JK flip flop?

What is JK Flip-Flop Excitation Table? JK Flip-Flop Excitation Table is used to trigger the flip flop. The flip flop must be excited or triggered by the excitation table to move from its current state to the next one. It was created by using the truth table.

How do you write an excitation table for flip flops?

Flip-flop excitation tables In order to complete the excitation table of a flip-flop, one needs to draw the Q(t) and Q(t + 1) for all possible cases (e.g., 00, 01, 10, and 11), and then make the value of flip-flop such that on giving this value, one shall receive the input as Q(t + 1) as desired.

What is the equation for the J K flip flop?

Characteristic equation for the J K flip-flop, Q(t+1)=J¯Q+¯KQ¯¯¯¯¯¯¯¯¯¯¯¯¯¯Q(t+1)=¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯(J¯Q+¯KQ=(¯J+Q)(K+¯Q)¯¯¯¯¯¯¯¯¯¯¯¯¯¯Q(t+1)=¯J¯Q+KQ.

Is JK flip-flop level triggered?

Asked 3 years, 4 months ago Viewed 901 times \$\begingroup\$ I started learning about latches and flip flops recently, and my understanding is that edge-triggered devices like flip flops ignore their inputs until the clock signal transitions from low to high or from high to low, depending. This timing diagram show the output of a falling edge D FF that I expected in a particular edge case Indeed, I found this very result with the following master-slave D FF simulated in software Then I learned about the JK flip flop and, while I understand what it’s supposed to do, I am confused about something. With the circuit above I tried something similar to what I did with the D FF : I expected Q not to change and stay low since J and K were not high when the clock transitioned from high to low. This is why I am confused : to me, this contrasts with other edge-triggered flip flops like the D or T, which only change their output based on what the inputs were at the transition of the clock signal (whether rising, falling, or both).

Here, the outputs of the JK FF only change at the falling edge, but even if the values of the inputs are the same at two consecutive falling edges, if they have changed in between then the output will reflect it. As I had understood, this is not what an edge-triggered devise should do. I believe it is due to the fact that this JK FF is realy two SR latches in series.

So as long as the clock is high, the master latch can capture the inputs but does not need them to be held until the clock does back to low. So the inputs are processed as long as the clock is high, but the output only changes on a falling edge. I also read that other flip flops can be implemented using JK flip flops, which I’d understand if this circuit did not behave that way. Having a circuit only acknowledges inputs on a clock edge is a desirable property, but this JK FF that is shown everywhere seems to not work that way. But again I only learned about them recently so maybe my confusion comes from the fact that I am missing something. Excitation Table Of Jk Flip Flop \$\endgroup\$ 1 \$\begingroup\$ You have discovered the drawback of the Master-Slave JK flipflop. The M-S JK flipflop is not edge triggered, it is pulse triggered. What you have discovered is a phenomenon which M-S JK flipflops suffer from known as ‘ones catching’. Excitation Table Of Jk Flip Flop You could look up ‘ones catching’ for more info. answered May 13, 2020 at 14:54 \$\endgroup\$ 2 \$\begingroup\$ Both D type and JK type flip flops can be designed to trigger on either the positive or the negative clock edge. However, perhaps for reasons of history, most 74 series TTL D type flip flops are positive edge triggered (74, 374, etc), and most JK type flip flops are negative edge triggered (112, 114 etc). Neil_UK Neil_UK 158k 3 gold badges 175 silver badges 388 bronze badges \$\endgroup\$ 3

What is JK flip-flop timing diagram?

JK Flip Flop Timing Diagram This is known as a timing diagram for a JK flip flop. In addition to the basic input-output pins shown in Figure 1, J K flip-flops can also have special inputs like clear (CLR) and preset (PR) (Figure 4). These can be used to bring the flip-flop to a definite state from its current state.

What is the excitation table?

In electronics design, an excitation table shows the minimum inputs that are necessary to generate a particular next state (in other words, to “excite” it to the next state) when the current state is known. They are similar to truth tables and state tables, but rearrange the data so that the current state and next state are next to each other on the left-hand side of the table, and the inputs needed to make that state change happen are shown on the right side of the table.

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How do you calculate flip-flops?

Characteristic Equation of T Flip-Flop –

The characteristic equation of the flip-flop is the algebraic representation of the next state of the Flip-Flop (Q n+1 ) in terms of the present state (Q n ) and the current input (T).That means, here the input variables are Q n and T, while the output is Q n+1, From the truth table, as you can see, the output Q n+1 is 1 for two different input combination of Q n and T.

Let’s write down these two input combinations in the K-map, and let’s try to simplify the Boolean expression. From the K-map, the two minterms are T Q n ‘ and T ‘ Q n, That means the characteristic equation of the T flip-flop is

What is the output of a JK flip flop?

What is J-K Flip Flop? J-K flip-flop can be treated as an alteration of the S-R flip-flop. J represents SET, and ‘K’ represents CLEAR. In the JK flip-flop, the ‘S’ input is known as the ‘J’ input, and the ‘R’ input is known as the ‘K’ input. The output of the JK flip-flop does not modify if both ‘J’ and ‘K’ are ‘0′. Excitation Table Of Jk Flip Flop The truth table of the JK flip-flop is displayed in the table.

S R Q N-1
1 1
1 1 $\overline }$

The logic symbol for the JK flip-flop is demonstrated in the diagram. Get certified by completing the course : What is J-K Flip Flop?

What is the difference between truth table and excitation table?

Excitation table lists possible inputs for a desired next output state from current output state. Truth table lists possible inputs and the corresponding output.

What is the behavior of J-K flip-flop?

Behavior – Each flip-flop stores a single bit of data, which is emitted through the Q output on the east side. Normally, the value can be controlled via the inputs to the west side. In particular, the value changes when the clock input, marked by a triangle on each flip-flop, rises from 0 to 1; on this rising edge, the value changes according to the corresponding table below.

D Flip-Flop T Flip-Flop J-K Flip-Flop S-R Flip-Flop
1 1


1 Q ‘


1 1
1 1 Q ‘


1 1
1 1 ??


Another way of describing the different behavior of the flip-flops is in English text.

D Flip-Flop: When the clock rises from 0 to 1, the value remembered by the flip-flop becomes the value of the D input ( Data ) at that instant. T Flip-Flop: When the clock rises from 0 to 1, the value remembered by the flip-flop either toggles or remains the same depending on whether the T input ( Toggle ) is 1 or 0. J-K Flip-Flop: When the clock rises from 0 to 1, the value remembered by the flip-flop toggles if the J and K inputs are both 1, remains the same if they are both 0, and changes to the K input value if J and K are not equal. (The names J and K do not stand for anything.) R-S Flip-Flop: When the clock rises from 0 to 1, the value remembered by the flip-flop remains unchanged if R and S are both 0, becomes 0 if the R input ( Reset ) is 1, and becomes 1 if the S input ( Set ) is 1. The behavior in unspecified if both inputs are 1. (In Logisim, the value in the flip-flop remains unchanged.)

Is J-K flip-flop positive or negative?

Description – The J-K Flip-Flop block models a negative-edge-triggered J-K flip-flop. The J-K flip-flop block has three inputs, J, K, and CLK, On the negative (falling) edge of the clock signal ( CLK ), the J-K Flip-Flop block outputs Q and its complement, !Q, according to the following truth table.

J K Q n !Q n
Q n-1 !Q n-1
1 1
1 1
1 1 !Q n-1 Q n-1

When J is 1 and K is 0, the flip-flop goes to the set state ( Q n is 1). When J is 0 and K is 1, the flip-flop goes to the reset state ( Q n is 0). When both J and K are 0, the flip-flop stays in the previous state ( Q n is Q n-1 ). When both J and K are 1, the flip-flop toggles ( Q n is the complement of Q n-1 ).

Is J-K flip-flop asynchronous?

Free RRB NTPC ASM CBAT Psycho Full Practice Set 1 (Easy to Moderate) 165 Questions 130 Marks 48 Mins The PRESET and CLEAR inputs of the JK Flip-Flop are asynchronous, which means that they will have an immediate effect on the Q and Q’ outputs regardless of the state of the clock and / or the J and K inputs, 1.When the preset input is activated, the flip-flop will be set (Q=1, not-Q=0) regardless of any of the synchronous inputs or the clock.2.When the clear input is activated, the flip-flop will be reset (Q=0, not-Q=1), regardless of any of the synchronous inputs or the clock.3.When preset and clear inputs are activated we get an invalid state on the output, where Q and not-Q go to the same state.

Input Output
Preset Clear CLK J K Q
Invalid 0 0 1* 1*
Preset 0 1 1 0
Clear 1 0 0 1
No change 1 1 Q 0 Q̅ 0
No change 1 1 0 0 Q 0 Q̅ 0
Reset 1 1 0 1 0 1
Set 1 1 1 0 1 0
Toggle 1 1 1 1 Q̅ 0 Q 0

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Is a J-K flip-flop rising edge?

Frequently Asked Questions (FAQs) – Some Frequently Asked Questions on JK Flip Flop are given below. Ques 1. What is JK Flip Flop full form? Ans. The JK Flip Flop full form is:

J – Jack K – Kilby It is named on the name of its inventor, Jack Kilby.

Ques 2. What is a JK flip-flop, and how does it differ from other flip-flops? Ans. A JK flip-flop is a type of sequential logic circuit that can store one bit of data. It differs from other flip-flops like the D and T flip-flops because it has two inputs: J (set) and K (reset), which can be used to toggle the output of the flip-flop.

  • Ques 3. What is the difference between a synchronous and asynchronous JK flip-flop? Ans.
  • A synchronous JK flip-flop has a clock input that controls when the inputs are sampled and the output is updated, while an asynchronous JK flip-flop has inputs that can change the output at any time, regardless of the clock input.

Ques 4. What is the difference between a positive-edge-triggered and negative-edge-triggered JK flip-flop? Ans. A positive-edge-triggered JK flip-flop changes its output on the rising edge of the clock signal, while a negative-edge-triggered JK flip-flop changes its output on the falling edge of the clock signal.

How do you calculate flip flop setup time?

Delay Characterization for Sequential Cell Kamalpreet Kaur, Nishant Madan, Syed Shakir Iqbal Freescale Semiconductor India Pvt. Ltd. Introduction With prior knowledge of delay characterization for combinational standard cells, where the delay values are dependent on the input slew and the output load, one needs to take in account of the propagation delay in picture.

  1. The scenario gets a bit complex when it comes to sequential elements.
  2. Modeling setup time, hold time, C-Q delay and various other factors add more complexity to the characterization to sequential elements.
  3. This paper discusses the models and methodology that are used commonly for characterizing the timing parameters of various sequential logic cells which are key elements of synchronous design.

Timing Parameters in a Sequential Cell While the timing parameters of a combinational cell are limited to min and max delays using the input transition, the output load and the timing model of the cell as a set of variables, sequential cells come up with their own set of complex timing checks.

Setup Time Hold Time Clock to Out (C-Q) Delay Min Pulse Width

Methodology for Finding the Sequential Delays of a Standard Cell With combinational element concerned only with the propagation delay of the cell, the sequential element are bit more complex in this scenario. With different arcs it is necessary to model setup time, hold time and c-q delay of a flop while modeling it into the library.

The number of arcs required to model can vary within the sequential elements. In this paper we will be discussing about the methodology to find the setup time, hold time or C-Q delay of flip-flops and latches. The min pulse width requirements as discussed in the previous section are a derivative of setup and hold time itself and hence will be implicitly covered.

JK Flip-Flop Explained | Excitation Table and Characteristic Equation of JK Flip Flop

a) Setup Time: Setup time is a common timing parameter associated with sequential devices. The setup time is used to meet the minimum pulse width requirement for the first (master) latch that makes up a flip flop. More simply, the setup time is the amount of time that an input signal (to the device) must be stable (unchanging) before the clock ticks in order to guarantee minimum pulse width and thus avoid possible meta-stability within the latching loop.

Setup time for Flip Flop:

Take a clock of pulse width 10ns i.e. a frequency of 100MHz Consider data transition from 0 → 1 at infinite setup time say 10ns before the active clock edge. Calculate the C-Q delay from 50% of clock to 50% of Output. Keep on bringing the data closer to the active edge of the clock. Calculate the C-Q delay for each input vector and check for 10% increase in C-Q delay. Note the difference of transition time between data input and the clock active edge. This will become the setup time of the flop.

Now, one question can arise is why a factor of 10% is taken for calculating the setup time? When we are taking the data transition closer to the active edge of the clock, at the instant when setup time is violated the system goes into a meta-stable state and the output takes longer time to settle down which is the reason for increased C-Q delay. Figure 1: Setup timing measurement for a positive edge triggered flip-flop. b) Hold Time: Hold time is also a timing parameter associated with all sequential devices. The Hold time is used to further satisfy the minimum pulse width requirement for the first (Master) latch that makes up a flip flop.

The input must not change until enough time has passed after the clock tick to guarantee the master latch is fully disabled. More simply, hold time is the amount of time that an input signal (to a sequential device) must be stable (unchanging) after the clock tick in order to guarantee minimum pulse width and thus avoid possible meta-stability.

This can be found out by using spice simulations and following the below mentioned steps:

Hold Time for Flip Flop:

Take a clock of pulse width 10ns i.e. a frequency of 100MHz Consider data transition from 0 → 1 at infinite setup time say 10ns before the active clock edge. Keep on bringing the data closer to the active edge of the clock. Time when the output makes a transition from 0→1, calculate the difference between the data arrival time and clock edge time that will give the hold time for the flip flop.

Figure 2: Hold timing measurement for a positive edge triggered flip-flop. c) Clock to Out (C-Q) Delay: Clock to out delay is generally considered at infinite setup time. With data making a transition at 10ns before the active clock edge, one can probe the two signals clock and output both at 50% of their voltage levels.

The difference between their transitions will give the clock to out or C-Q delay for the flip flop. d) Min Pulse Width: Min pulse width is defined as the minimum permissible pulse width values for both high and low levels below which a given sequential element like flip-flop, latch or SRAM cell will fail to work.

It signifies the minimum time these cells will take to function and provide the correct output while being operated. For simulation purposes it is simply another form of representing setup and hold time corresponding to the concerned clock edge and hence can be characterized for different output loads, input slews and triggering events similar to setup and hold time. Figure 3: Min Pulse Width and its relationship with setup and hold time. One key point to note here is that all the SPICE deck analysis involved must be performed for both rise-to-rise and fall-to-fall data transitions for the flip flop as the RC delay parameters and the signal paths vary with respect to the value of data itself.

So far all the analysis discussed above has been with a flip-flop or an edge triggered element as a reference. While the definition of setup/hold time and C-Q delay remain same for latches as well, however with the latches being level triggered devices instead of edge triggered, the concept to extract the timing parameters of latch are a bit more tricky.

In case of a latch, we need to understand the opening and closing windows for data sampling instead of just a simple edge. Let us consider the timing in a negative level triggered latch as shown in figure 4. The latch will remain transparent in case of a low clock signal while the state will be latched otherwise.

  • Thus, there is an opening window for data sampling when the clock goes low and a closing window when the clock goes high.
  • Now let us add the considerations for setup and hold time into this.
  • Since the circuit elements take a finite time to sample a data in, hence for hold time, the timing requirement is limited with the closing of the latch window (shown in blue in figure 4).

This requirement is the same as that in case of a positive edge triggered flip-flop and hence the same setup can be used to measure the hold time. For the case of setup timing, there are two scenarios; setup timing at the opening window and setup timing at the closing window. Figure 4: Setup and hold timing for a positive edge triggered flop and negative level triggered latch. The reason for this check is that unlike a flop, the latch output is not a fixed value during a static clock level. For example, when clock is low, the flop output remains a constant value from the previously captured data, while in case of a negative latch; the output is same as the input data at that instance.

Hence, we have a burrow margin which can be given to data path connected at the output of latch, provided we have ensured correct setup timing with the same setup time as at the closing window near the opening edge as shown in figure 3. Hence, to characterize a negative level triggered latch, the characterization methodology is the same as than in case of a positive edge triggered flop and a similar scenario exists for negative edge triggered flop and positive level triggered latch.

Conclusion This paper elucidates the methodologies followed for setup analysis; hold analysis and setup dependent hold and hold dependent setup analysis. Discussing on the areas of C-Q delays it traverses from setup time to min pulse width checks too for sequential elements flops and latches.

Which IC is used in JK flip-flop?

The 7476 is a master—slave J-K and the 74LS76 is a negative edge-triggered J-K flip-flop. Both chips have the same pin configuration. Both chips have synchronous inputs of J, K and Cp.

What is the clock frequency of a JK flip-flop?

A J-K flip-flop with J = 1 and K = 1 has a 20 kHz clock input. The Q o As one flip flop is used so there are two states available. So, 20/2 = 10Hz frequency is available at the output.

Is the 74LS76 JK flip flop a level triggered or edge triggered?

The 7476 is a master—slave J-K and the 74LS76 is a negative edge-triggered J-K flip-flop. Both chips have the same pin configuration. Both chips have synchronous inputs of J, K and Cp.

Which triggering is used in JK flip flop?

Negative edge-triggered JK flip flop: In negative edge triggered flip flops the clock samples the input line at the negative edge (falling edge or trailing edge) of the clock pulse.

What is the toggle condition in JK?

Solution: – A J-K flip flop happens to be toggled when both input J and K are high or true or set at 1. When J and K are tied together or set at 1 then the present state is equal to the previous state and gets complimented that 0 becomes 1 or 1 becomes 0. Therefore, a J-K flip flop made to toggle_? is J=1,K=1, Hence, option (D) is the correct answer.