Mana PAPER No.-2.3 SBCA COMPUTER ORGANIZATION UNIT-1 1.Definc Logical circuit. Discuss different types of logical circuits? ANSWER: There are two standard forms of binary variable or this circuits operate an binary variable that assumes one of the two distinct values, usualy called 0 and 1. This logic circuit ontains diferent types of logic like AND logic. OR Iogic, NOT logic etc AND LOGIC LOGIC CIRCUT Information and digital system is represented and process by electronic networks called logic circuit In AND logic f both the binary inputs are high then only the output wilbe high. AND logic represented by a symbol called muitiplication sign. B B Y (A.B) 0 0 0 1 The above logical AND operation takes place between two Boolean variables A and B is written as Y = (A.B) AND logic is also called as conjuction. oRLOGIC In OR logic if only one of the input is high then the output will be high. If Both the input is low, so it will produce a low output. OR logic represented by a symbol" called Addition sign. OR logic is also called as Disjunction. Y Y (A B) 0 0 PRESIDENCY COLLEGE Mant? PAPER NO SBCA cOMPUTER ORGANIZATION SBCA The above logical OR logic trthtable takes place between wo Boolean variables A and B is written as Y= (A+8) NOT LOGIC This logic often regarded as an inverter Not logic just invertes the current logic input which means high bocomes low and low becorma hit is represented as bar symbol that is 'A'. high. t A A Not logic is also called as Negetion. X-OR LOGIC In this logic if both the input are high or low then the output will be low, or if both the inputs are of same kind then the output is low. It is denoted as a symbol A+B Y A8 1 0 0 A+B A B+AB NAND LOGIC This logic consist of AND and NOT operation. NAND logic just the inverse of AND logic. There is a Not operation perform the output which involves the logical value. It is representd as A.B A.B B 2 PRESIDENCY COLLEGE PAPER NO.-2.3 COMPUTER ORGANIZATION 2.3 SBCA A B A.B 0 0 1 NOR LOGIC: NOR logic consist of a OR operation and Not operation., just exactly inverse of OR operation. A+B B B A+B 0 0 0 1 2.What is K-map? Drawa k-map for the following expression A BCD+ AB cD +ABCD +ABCD +ABCD +ABCD+AB CD +ABCD ANSWER: K- map means kernough map. A K-map provides a pictorial or optical method of grouping together expression with common factors and therefore eliminating unwanted variables. The K-map can also be described as a special arrangement of a truth table. ABCD+ CD +ABCD +ABCD+ABCD +ABCD+ABCD +ABCD B C 0 0 0 0 0 0 0 0 coLLEGE SBCA APER NO COMPUTER ORGANIZATION SBCA 0 Digital 0 0 0 1 (Truthtable of K-Map expression) 00 01 0 00 01 0 0 11 10 (K map Diagran Group-1:- D 0 0 1 0 1 0 0 In the above truth value, common factor is A B Group-2 8 D 1 0 1 1 1 0 1 0 In the above truth value, common factòr is AC Group-3- C D A o 1 0 1 0 0 0 1 1 Here the common factor is B D.So, after minimizing the K-map expression the common values are (A B+A C+BD) 4 PRESIDENCY COLLEGE SBCA COMPUTER ORGANIZATION PAPER NO.-2.3 Dgial couniers consisis of many Fipfiops. A regisier that goes through a predefined sequence of state upon the application of input pulses is called a counter The input pulses may be clock pulses or may be originated from any external source. Ouniers are used to count certain event, electrical pulses proportional to the event are produced for the counting purpose. It can also be used to cout time intervals or frequency. 3.Define counter explain the different types of counter ANSWER: There are basically two types of counters i. Synchronous counter i. Asynchronous counter in a synchronouS CDunter al fiplops are clocked simutaneously on the other hand in Asynchronous counters the fiplops are nat clocked simultaneously instead of it each Flipflop is triggered by the previous flipflop. SYNCHRONOUS COUNTER In this counters all the flipflops are directly clocked at the same time so that all the flipflops change their output at the same time. To over come the problem of glitches (unwanted pulses) occurs at the output gate, Synchronous counters are developed. >This counters are also known as parallel counters. ASYNCHRONOUS COUNTER A binary asynchronous counter can be realized by the use of a edge triggered J-K Flip-flop, where the flip-flop are connected in series The output of one flipflop is connected to the clock terminal of the next flip-flop. In other words the output of one flip-flop drives the next flipfilop, so it is called serial counters >This type of counters are slow in operation due to series connection. >It is also called as ripple counter because the triggers moves through the flip-flops like a ripple in water so it is called as ripple counter. >The ripple counters are used to decoding gate which detects a given state of the counters and produces an output when that state is detected. Ripple counters are very simple to built but they are not suitable for high frequency application. Normaly ripple counters are used as frequency devider. COunt clock pulse J Ki Q2 Counter enable clear pin (Asynchronous counter) PRESIDENCY COLLEGE SBCA PAPER N0.-2.3 SBCA cOMPUTER ORGANIZATION PRE-SETABLE COUNTERS A pre-setable counter starts counting from a number greater then zero, this no. can be set before counting start. UP-COUNTERS Ifa counter count upward towards a higher number. DOWN COUNTER Ifa counter which count downward towards a lower number. JPDOWN COUNTER A counter which is designed to count either tow a higher number or towards a lower number is called up-down counter. 4.What is f1lip-lop? Explain master -slave fip-f1op? ANSWER: FLIPFLOP The storage element employed in a clock sequential circuit is called Flipflop. A flipflop is a binary shell capable of storing one (1) bit of information. A flipflop is a bistable device, It has two stable states, it's output remain either high or low which means an output for a normal value and the other one is for the complement value. A flipfilop maintains a binary state until derected by a clock pulse to switch state. The high stable states that is one called SET and the other table state (LOW) that is Zero called RESET. The diference among various type of flipflop is in the number of input is progresses and in the manner in which the input effects the binary states. Basically flipfiops are of 2 types. 1) Master- slave Flipflop 2) Edge-triggered Flipflop Inputs Normal O/P Inverted OP (Block diagram of a flip-lop) ter-slave Flipflop A master- slave Flipflop is constructed from two separale Flipflop Y1 Q Y NCY COLLEGE 6 BCA COMPUTER ORGANIZATION PAPER N0.-2.3 One circuit serves as master and other is like a slave. The logic diagram of Master-slave flip-flop is consisting of two different flip-fops. The master Flip-flop is enable on the positive edge of the clock pulse and the slave flip-lop is disable by the inverter (Not gate). The information at the S, Rinput is transmitted to the master flip-lop, when the pulse returns to Zero, the Master flip-flop is disable and the slave 1up-1iop Is enable. The slave flip-flop then goes to the same state as the Master flip-lop. 5. What is register explain shift register? ANSWER: An individual tlip-flop can be used to store one bit. However, in machines in which data are handled in words consisting of many bits (perhaps as many as 64), it is convenient to arrange number of flip-flops into a common structure called register. F1 F2 F3 F4 a D D D D Shft regsters are important digital biocks that can be used to slore binary data. They can accept data in either a serialinput or a paralel format and can, likewise, deliver data in either serial or paralle. There are thus four basic four basic register types: serial input-seial output, serial input-parallel output, parallel input-serial output, and parallel input-parallel output. In one application the register can be used to change data from a serial fomat into a parallel format, or vice versa. As, such shift registers can be regarded as data format changers. There are a great many other shift registers applications- arithmetic operations, logical operations, and counters, to name only a few. Parallel shift data bits are shited simultaneously with a single clock transition. Register capacity by the number of flip-lop in the register. There must be one fip-tiop for each binary bit; the register capacity is2 where n number of fip- flops. Serial shit data bits are shifted one after the other in seial fashion with one after other in a serial fashion with one bit shited at each clock transition. Therefore n clock transition is needed to shift an n-bit binary number. Shift register a group of flip-flop connected in such a way that a binary number can be shifted into or out of the flip-lops. 6. Write a short note on: a. Counter b. Multiplexer ANSWER: a Counter: A counter has a natural count of 2n, where n s the number of fip-fop in the counter. Counlers of ary modules can be construcled by incorporating logic which causes certain states to be skipped over or omited. One technique for skipping counts is to steer the clock pulses to certain fip flop at the proper time- this is called string logic. Logie can be included such that the counter can operate in either a countup or counl-down mode. Furthermore logic gates can be designed to uniquely decode each state of a counter. Higher module counters can be easlly constructed by using combinations of lower modulus counters. Such configurations represent a compromise between speed and hardware count. The shift count s has the great advantage of simplfed decoding. This type of counter does, however, have undesired states, and these must be provided for in the counter design. b. Multiplexer Multiplexer means many into one. A mutiplexer is a circut with many inputs but only oulput. By applying control signals, we can steer any input to the output The circuit has n inputs signals, m control signals, and 1 output signal. One of the popular mutiplexer is the 16 to 1 mutiplexer which has 16 input4 control bits, and 1 output bit. Amultiplexer isa rcult ith many inpul bis and one autput. The 16-t0-1 muliplaxer has 16 input bits, 4 combol bis, and 1 output bi. The 4 conrol bis select the steer 1 of the 16 inputs to the output. The mutiplexes a universal logic circut because it can generate any truth table. A de-muiplexer has many inputs and many outputs. By applying control signalis we can steer the input signals to one of the output ines. A decoder is sinlar to a de-multiplexer, excapt hat there is no data input.The control bits are the only input. They decided by actvating one of the output ines. PRESIDENCY COLLEGE