Question

An asynchronous sequential circuit is described by the following excitation and output functions
Y=X1X2+(X1+X2)Y
Z=Y
A) draw the logic diagram
B) derive the transition table and output map
C) describe the behavior of the circuit

Answer 1

UNIT -41. An asynchronous sequential circuit is described by the following excitation andoutputfunctions (16)Y = x1x2'+(x1 + x2' )yZ = y(i) Draw the logic diagram of the circuit.(ii) Derive the transition table and output map.

(iii) Obtain 2 state flowtable.(iv) Describe in words the behaviour of the circuit.2.a) Explain the types of hazards in digital circuits.

(10)b)Implement the switching function F=∑m(1,3,5,7,8,9,14,15)bya static hazard free 2level AND-OR gate network.(6)3. Describethesteps involved in design ofasynchronous design .

Explain with the help ofT-flip-flop design. (16)4. a)What is the objective of state assignment in asynchronous circuit?Explain race freestate assignment with an example (8)5.

Develop the state diagram and primitive flow table for a logic systemthat has 2 inputs, x and y and an output z. And reduce primitive flowtable. The behaviour of the circuit is stated as follows. Intially x = y =0.Whenever x=1 and y=0 then z=1, whenever x=0 and y=1 thenz=0.When x=y=0 or x=y=1 no change in z it remains in the previousstate.

The logic system has edge triggered inputs without having clock.The logic system changes state on the rising edges of the 2 inputs. Staticinput values are not to have any effect in changing the z output.(16)6.Write a detailed note on Race free state assignment (16)7.

What is the objective of state assignment in asynchronous circuit? Givehazard free realization for the Boolean functionsF(A,B,C,D)=∑m(0,2,6,7,8,10,12)8.Find the static and dynamic hazard free realization for the followingfunction usingi)NAND gatesii)NOR gates f(a,b,c,d)=∑m(1,5,7,14,15Page3of4