digital principles and system design two marks

 

Multiplexing means transmitting a large number of information units over asmaller number of channels or lines.60.What is Demultiplexer?A Demultiplexer is a circuit that receives information on a single line andtransmits this information on one of 2

n

possible output lines.61.Give the truth table for a half adder.Input OutputX Y Sum ( S ) Carry ( C )0 0 0 00 1 1 01 0 1 01 1 0 162.Give the truth table for a half Subtractor.Input OutputX Y Borrow( B ) Diffe ( D )0 0 0 00 1 1 11 0 0 11 1 0 063.From the truth table of a half adder derive the logic equationS = X

⊕⊕⊕⊕

YC = X . Y64. From the truth table of a half subractor derive the logic equationD = X

⊕⊕⊕⊕

YB = X

1

. Y65.From the truth table of a full adder derive the logic equationS = X

⊕⊕⊕⊕

Y

⊕⊕⊕⊕

ZC = XY + YZ + XZ66.What is code conversion?If two systems working with different binary codes are to be synchronized inoperation, then we need digital circuit which converts one system of codes to theother. The process of conversion is referred to as code conversion.67.What is code converter?It is a circuit that makes the two systems compatible even though each uses adifferent binary code. It is a device that converts binary signals from a source codeto its output code. One example is a BCD to Xs3 converter.68.What do you mean by analyzing a combinational circuit?The reverse process for implementing a Boolean expression is called asanalyzing a combinational circuit. (ie) the available logic diagram is analyzed stepby step and finding the Boolean function69.Give the applications of Demultiplexer.

 

i) It finds its application in Data transmission system with errordetection.ii) One simple application is binary to Decimal decoder.70.Mention the uses of Demultiplexer.Demultiplexer is used in computers when a same message has to be sent todifferent receivers. Not only in computers, but any time information from onesource can be fed to several places.71.Give other name for Multiplexer and Demultiplexer.Multiplexer is other wise called as Data selector.Demultiplexer is otherwise called as Data distributor.72.What is the function of the enable input in a Multiplexer?The function of the enable input in a MUX is to control the operation of theunit.73.Give the truth table for a full Subtractor.Input OutputX Y ZBorrow ( B)Diffe ( D )0 0 0 0 00 0 1 1 10 1 0 1 10 1 1 1 01 0 0 0 11 0 1 0 01 1 0 0 01 1 1 1 174.Give the truth table for a full adder.Input OutputX Y Z Sum ( S ) Carry ( C )0 0 0 0 00 0 1 1 00 1 0 1 00 1 1 0 11 0 0 1 01 0 1 0 11 1 0 0 11 1 1 1 175.From the truth table of a full subtractor derive the logic equationS = X

⊕⊕⊕⊕

Y

⊕⊕⊕⊕

ZC = X

1

Y + YZ + X

1

Z76.What is priority encoder?A priority encoder is an encoder that includes the priority function. Theoperation of the priority encoder is such that if two or more inputs are equal to 1 atthe same time, the input having the highest priority will take precedence.77.Can a decoder function as a Demultiplexer?

 

Yes. A decoder with enable can function as a Demultiplexer if the enable lineE is taken as a data input line A and B are taken as selection lines.78.List out the applications of multiplexer?The various applications of multiplexer area. Data routing.b. Logic function generator.c. Control sequencer.d. Parallel-to-serial converter.79.List out the applications of decoder?The applications of decoder area. Decoders are used in counter system.b. They are used in analog to digital converter.c. Decoder outputs can be used to drive a display system.80.List out the applications of comparators?The following are the applications of comparatora. Comparators are used as a part of the address decoding circuitry incomputers to select a specific input/output device for the storage of data.b. They are used to actuate circuitry to drive the physical variable towards thereference value.c. They are used in control applications.81.What are the applications of seven segment displays?The seven segment displays are used ina. LED displaysb. LCD displays82.What is digital comparator?A comparator is a special combinational circuit designed primarily tocompare the relative magnitude of two binary numbers.INPUTSA BA>B A=B A<BOUTPUTSBlock diagram of n-bit comparator

n-bitcomparator

the positive or negative going transition of the pulse based on the triggering of thepulse.176.Define bit time and word time.The time interval between clock pulses is called bit time.The time required to shift the entire contents of a shift register is called wordtime.177.What is bi-directional shift register and unidirectional shift register?A register capable of shifting both right and left is called bi-directional shiftregister.A register capable of shifting only one direction is called unidirectional shiftregister.178.Define equivalent state.If a state machine is started from either of two states and identical outputsequences are generated from every possible set of sequences, then the two states aresaid to be equivalent.179.If a shift register can be operated in all possible ways then it is called as-----------Ans: Univerasal register: It can be operated in all possible modes with bi-directional shift facility.180.What is gate delay?If the change in output is delayed by a time

εεεε

with respect to the input. Wesay that the gate has a propagation delay of 

εεεε

. Normally propagation delay for 0 to 1output (

εεεε

1) may be different than the delay for 1 to 0 changes (

εεεε

2).181.Define state reduction algorithm.State reduction algorithm is stated as “Two states are said to be equivalent if,for each member of the set of inputs they give the same output and send the circuiteither to the same state or to an equivalent state. When two states are equivalent,one of them can be removed without altering the input-output relation.182.What is meant by level triggering?In level triggering the output of the flip-flop changes state or responds onlywhen the clock pulse is present.183.Write the uses of a shift register.i) Temporary data storage.ii) Bit manipulations.184. What is meant by flow table?During the design of asynchronous sequential circuits, it is moreconvenient to name the states by letter symbols without making specificreference to their binary values. Such a table is called a flow table.

 

185. What are the problems involved in asynchronous circuits?The asynchronous sequential circuits have three problems namely,a. Cyclesb. Racesc. Hazards186. Define cycles?If an input change includes a feedback transition through more thanunstable state then such a situation is called a cycle.187. Define primitive flow table?A primitive flow table is a flow table with only one stable total state ineach row. Remember that a total state consists of the internal state combinedwith the input.188. Define merging?The primitive flow table has only one stable state in each row. The table can bereduced to a smaller numbers of rows if two or more stable states are placed in thesame row of the flow table. The grouping of stable states from separate rows intoone common row is called merging

Posted in: digital principles and system design