subject is digital 1

Sequential Logic Circuits use flip-flops as memory elements and in which their output is dependent on the input state :

Design Specifications There are three traffic light signals (S1, S2, and S3), each alternating between three states, RED, YELLOW and GREEN. These signals control the traffic flow on the three roads, road1, road2, road3. Your traffic controller should operate in two mode: Day and Night. In Night mode all traffic light signals show intermittent amber light (YELLOW).

The operation of the three light signals (S1-S3) is controlled through an arrangement of traffic sensors and traffic light controller circuit. There are three traffic sensors X1, X2 & X3, which sense the presence of traffic on the roads 1-3 as illustrated in Table 1. The controller operation is determined by the output of these three sensors as enumerated in Table 1.

Table 1. Traffic Sensors and Controller Operation Traffic case Controller operation X3 X2 X1 000 001 010 All roads have no traffic Only Road 1 has traffic Only Road 2 has traffic Roadl and Road2 have traffic 011 100 Only Road3 has traffic Road1 and Road3 have traffic 101 Stay at STATE 7 Stay at STATE 1 Stay at STATE 2 Alternate between STATE 1, STATE 4, STATE 2, STATE 5, STATE 1.... Stay at STATE 3 Alternate between STATE 1, STATE 4, STATE 3, STATE 6, STATE 1.... Alternate between STATE 2, STATE 5, STATE 3, STATE 6, STATE 2... Normal operation: STATE 1, STATE 4, STATE 2, STATE 5, STATE 3, STATE 6, STATE 1.... 110 Road2 and Road3 have traffic 111 All roads have traffic Table 1. Traffic Sensors and Controller Operation Traffic case Controller operation X3 X2 X1 000 001 010 All roads have no traffic Only Road 1 has traffic Only Road 2 has traffic Roadl and Road2 have traffic 011 100 Only Road3 has traffic Road1 and Road3 have traffic 101 Stay at STATE 7 Stay at STATE 1 Stay at STATE 2 Alternate between STATE 1, STATE 4, STATE 2, STATE 5, STATE 1.... Stay at STATE 3 Alternate between STATE 1, STATE 4, STATE 3, STATE 6, STATE 1.... Alternate between STATE 2, STATE 5, STATE 3, STATE 6, STATE 2... Normal operation: STATE 1, STATE 4, STATE 2, STATE 5, STATE 3, STATE 6, STATE 1.... 110 Road2 and Road3 have traffic 111 All roads have traffic