 Hello everyone, welcome to this session on flip-flop design. In today's session we are going to design a T flip-flop or you may call it as a flip-flop conversion also using JK flip-flop. So, at the end of this session you will be able to discuss the operation of T flip-flop. T flip-flop is also called as a toggle flip-flop. Discuss the general model used for flip-flop conversion or design T flip-flop using other flip-flops. So, we already know that we are designing all the basic flip-flops using a generic latch structure. That is why you can call this process also conversion flip-flop conversion. So, let us understand what is a T flip-flop. So, T flip-flops comes with two mode store mode and toggle mode. In store mode T flip-flop stores the last state whereas in toggle mode the output of the flip-flop always toggle between 0 and 1. So, toggle flip-flop changes its state on every clock edge of the clock. So, in the toggle mode frequency of the queue is half of the input clock frequency. So, that is divided by 2. So, because of this most often this flip-flop is used in counters and frequency divider circuits. So, the function table is shown on the right side of the slide where inputs are like clock and T where outputs are the next state of flip-flop. So, on the edges of this clock if the T is 0 the next state is always the last state. So, no change will be there if T is equal to 0, but if T is equal to 1 the output is always complement of the last state ok. So, you can call this as a next state is always complement of the present state. On the left hand side two symbols are shown of T flip-flops. The first symbol is positive is triggered T flip-flop whereas second symbol is negative is triggered T flip-flop. Now, let us revisit the general model which we are going to use for flip-flop conversion. We are using JK flip-flop to design T flip-flop. So, next state is the conventional logic circuit which accepts external inputs and present state of the flip-flop provided. So, this next state logic is always used to generate excitation inputs required for the given flip-flop and this is how you can achieve the flip-flop conversion. The excitation inputs must be provided to the given flip-flop to obtain the definite next state as per the given specification. So, in this case as per the T flip-flop function table. The new flip-flop which you are going to design inherits the triggering mechanism of the given flip-flop. So, if you are using here negative is triggered flip-flop, negative is triggered JK flip-flop then you are going to design a negative is triggered T flip-flop. If you use here positive is triggered JK flip-flop then you are going to design a positive is triggered T flip-flop. Now, let us go through the steps to design or to convert the flip-flop. So, we are first going to modify our general model as per the specifications given. So, we are going to design a T flip-flop using JK flip-flop. So, we are going to modify our general model as per this specification. So, here the next state logic will accept T input and the present state of JK flip-flop to generate the excitation inputs for the JK flip-flop. We are considering here negative is triggered JK flip-flop. So, that is why we are going to design a negative is triggered T flip-flop. Now, for designing we required a conversion table you you may call it as a state synthesis table to derive the excitation inputs of the given flip-flop. So, this table is derived from the characteristic table of T flip-flop and the excitation table of JK flip-flop that is given in our case. So, this is the characteristic table of T flip-flop. You can pause the video and please write down the excitation table of JK flip-flop which is required for deriving the conversion table for this design problem. So, this is the JK flip-flop excitation table. So, we are going to design a conversion table using these two tables by combining these two tables. So, the first part of conversion table is nothing but the characteristic table of your T flip-flop. So, JK flip-flop excitation table identifies the JK input combinations for the required Q to QT plus 1 that is present state to next state transition as per the characteristic table of T flip-flop. So, the conversion table the first part is nothing but your characteristic table of T flip-flop whereas, the last two columns are the JK excitation inputs. So, 0 to 0 the excitations required for JK flip-flop is 0x, 1 to 1 that is present state 1 next state 1 excitations required for JK flip-flop is x 0, present state 0 next state 1 the excitation required is 1x, present state 1 next state 0 the excitation inputs required for JK flip-flop is x 1. So, this is how you can actually derive the conversion table required for this design. Now, let us use this conversion table to derive the J and K inputs. So, for that purpose we are going to use K map. So, with the K map we will derive the output expressions of the next state combinational logic that is J and K. So, first we will derive the J expression. So, we will map this J column on the K map. So, two variable K map is used here. So, T is used for column Q is used for rows. So, after mapping this J column on this K map you will find that a pair is possible. So, after grouping this 1 with this do not care case you will create a pair here and the expression for this pair is nothing but T. So, the expression for J we derived here is a T. Similarly, we will go for the K expression. So, let us map this K column on the K map. So, 0 x x 1. So, 0 x x 1. So, after grouping this mean term 3 with do not care case we will have here a pair again and the expression for this pair is T. So, here we have derived J and K expressions which in this case is T, J is equal to T and K is equal to T. Now, we will replace these expressions in our block diagram which we have learned in the last slides. So, here we do not require any hardware actually we can just use one wire we can short the J and K inputs and we can name it as a toggle input. So, let us draw the final logic diagram with the next state logic output expressions. So, here J and K inputs are shorted together and the name is given to this input is toggle that is T. So, here to convert JK flip flop to T flip flop no extra hardware is required only a wire is required which you can use to short J and K terminals. So, JK flip flop can be used as toggle flip flop just shorting the J and K inputs. So, this is how you can actually design a T flip flop using JK flip flop. So, you can repeat this process for designing T flip flop using any other flip flop. For example, T flip flop using SR flip flop or T flip flop using D flip flop or T flip flop using any other flip flop. So, these are the references you can go through for further reading. Thank you.