 Hello and welcome to the video lecture on introduction to shift resistors. Learning outcomes are at the end of this session students will be able to describe the working of different shift resistors and they will be able to design the circuits containing D type flip flops to form the different shift resistors. So, before moving towards concept you should recall the design and working of D flip flop. So, first we will see what is a resistor. So, resistor is a set of flip flops used to store the binary data and its function is to hold the information within the digital system so that it is available to the logical elements during computing process. Now, we will see what is a shift resistor. So, basically the shift resistor is a type of resistor that is applicable for moving the information upon the occurrence of clock signals. So, it is used basically for storage and transfer of digital data. There are two types of data transfer. So, first is serial data transfer in which the data is shifted along a single line one by one that is one bit at a time and the second type is parallel transfer. In this all the bits can be moved along the multiple paths towards the receiver. So, according to the possible ways resistors can be categorized as serial in, serial out, serial in parallel out, parallel in serial out and parallel in parallel out. So, we will see the function of these shift resistors one by one. First we will see the serial in, serial out, shift right, shift resistor. So, shift right means here the bits are shifted towards right one by one according to the given clock pulse. Here the block diagram shows 4 bit serial in, serial out, shift right, shift resistor. 4 D flip flops are used here, flip flop 1, 2, 3 and 4. Here the input is given to the leftmost D flip flop and the output of that is connected to the next D flip flops input. Means here each and every flip flops output is connected to the next D flip flops input. So, let us consider one data that is 1 0 1 0. We have to move this data towards the right one by one bit. So, at first clock pulse 0 will appear at the output of first flip flop. Then at the next clock pulse the 0 is shifted towards right as it is a input of second flip flop. So, 0 will be at flip flop 2 and the output of flip flop 1 will be the new bit that is 1. At the third clock pulse the data will be 0 1 0 and at the fourth clock pulse data will be 1 0 1 0. So, it works in serial manner to shift the data towards right hand side. So, total we will require 8 pulses to input the data serially and to drag out the data serially. The next type is shift left, shift resistor. So, we will keep the structure of D flip flops constant according to the shift right resistor just we have to connect the output of the next flip flop to the input of previous flip flop. For example, we will select the right most flip flop first and we have to give the serial input from right hand side. Now, the flip flop force output will be given to flip flop number 3 that is D 3. The output of flip flop 3 is given to input of flip flop 2. Like that the output of next flip flop is nothing, but the input of previous flip flop. Now, we will consider the left most bit that is 1 as a input. So, after that at second clock pulse the bit is shifted towards left that is the new bit arrives at flip flop 4 and its previous bit is shifted towards left. So, the output will be 1 0. Now, at the third pulse the output is 1 0 1 and at the fourth pulse the output is 1 0 1 0. So, totally 8 pulses are required means the 4 pulses are required to load that resistor with the input data and 8 pulses are required to drag out the output from these resistors. The next type is serial in parallel out shift resistor that is C4 resistor. Here you can see the 4 D flip flops are arranged again in cascading manner means the output of first flip flop is given to the input of next flip flop. Like that the 4 flip flops outputs are connected towards to the next flip flops inputs, but the outputs are collected simultaneously. For example, if we consider 1 0 1 0 then the bits are shifted towards right 1 by 1 within the 4 pulses and at the fifth pulse the data will arrive at the output that is 1 0 1 0 simultaneously. So, totally 5 pulses are utilized to see the data at the output. The next type is parallel in serial out shift resistor. Here you can see the 4 D flip flops are arranged in a specific manner. The constructions of AND gates and OR gates are required here to select the data to be shifted or to be loaded. So, there is one input provided shift or load bar. Here if we give the input 0 it will enable the operation of loading the data into the D flip flops means the data can be loaded simultaneously as it is parallel in operation. So, by making it enable we can load the data through D 0, D 1, D 2 and D 3 in respective flip flops. If we give 1 to the line shift or load bar then it will enable the shift operation through this AND gate G 4, G 5 and G 6. So, it will enable to shift the data. The first clock will give the data D 0 towards Q 0. At the second clock the D 0 will be shifted through G 4 to input of D of the second flip flop and at the third it will shift towards right through G 5 which is the input of flip flop 3. Like that the bits are shifted towards right on the available clock pulses. Now, I will request to pause the video and you have to think about this. How many clock pulses are utilized for shifting the data into and out of the piece of shift resistor? You can refer the previous diagram. Welcome back. So, the answer is 5 clock pulses because by shifting the data into shift resistor by shifting the data we can drag the outputs from the registers in 4 clock pulses and by 1 clock pulse we can load all the data simultaneously. So, we will require totally 5 clock pulses. Next is parallel in parallel out shift resistor that is PPO. Here also you can see the 4 bit parallel in parallel out shift resistor having the structure of 4 D flip flops, but the inputs and outputs are individual. Here the clock is common so the circuit is against synchronous, but you have to give the data simultaneously that is parallelly. So, we will again consider the data input 1 0 1 0. We will give this data parallelly through the input D 0, D 1, D 2 and D 3 in single clock pulse and at next clock pulse we can drag all the data from the system simultaneously that is 1 0 1 0 means totally 2 clock pulses are required for parallel in parallel out shift resistor. So, these are the working and constructions of the respective shift resistor types. So, we will see modes of operation. So, it is just summary what we have seen till now. So, these are the mode of operations. First is CISO right that is serial in serial out right which can be illustrated in this manner. Here the data can be shifted towards right and the data bits are shifted from left to right by 1 bit. Then CISO left here the data bits can be shifted towards left by 1 bit according to the clock pulses. The third type is CPO that is serial in parallel out. So, here the data can be shifted serially, but it can be dragged out within a single pulse simultaneously. Next type is PPO that is parallel in parallel out where all the data can be shifted in the resistors parallelly and output can be dragged parallelly. So, that is parallel in serial out. Here the data can be moved into the resistors parallelly, but the data can be dragged out in serial manner. So, totally 5 pulses are required. So, according to the shift modes there are different applications of the shift resistors. So, first is bi-directional shift resistor. So, it is serial in serial out shift resistor which accepts the data and moves the data towards right to left or left to right. And the second is rotate right shift resistor here. The data can be rotated towards right by shifting the data towards right. The last type is rotate left shift resistor. The data can be shifted towards left and it can be rotated again to go towards left. We will see the applications in next lecture. Thank