You are asked to design a light-bulb sequencing circuit. As shown in Fig. 1, the

ID: 1812282 • Letter: Y

Question

You are asked to design a light-bulb sequencing circuit. As shown in Fig. 1, the circuit takes as input a

16 Hz oscillator (or clock) and it must illuminate eight light bulbs from right to left, one at a time, one per

second . This process repeats itself forever.

(b)

Fig. 1: A high-level schematic of the light sequencer.

The circuit shown in Fig. 1(a) can be developed as a set of circuits shown in Fig. 1(b). The pulse generator

circuit accepts a 16 Hz pulse and converts this signal to a 1 Hz pulse, that is, a clock signal once every

second. This signal is then used to drive a counter that controls how the lights are illuminated.

%u2022 Develop Circuit 1 and Circuit 2 as sequential circuits using the minimum number of D flip-flops and

the minimum number of external gates.

%u2022 The job of Circuit 2 is to set the values of the control lines appropriately to drive the combinational

logic in Circuit 3. Design the combinational logic circuit that controls the light bulb bank using the

minimum number of 2 x 4 decoders and the minimum number of external gates.

CIRCUIT 3 IS BASICALLY 3;8 DECODER

Control lines output

s1 s2 s3 b7 b6 b5 b4 b3 b2 b1 b0

0 0 0 0 0 0 0 0 0 0 1

0 0 1 0 0 0 0 0 0 1 0

0 1 0 0 0 0 0 0 1 0 0

0 1 1 0 0 0 0 1 0 0 0

1 0 0 0 0 0 1 0 0 0 0

1 0 1 0 0 1 0 0 0 0 0

1 1 0 0 1 0 0 0 0 0 0

1 1 1 1 0 0 0 0 0 0 0

Y= b0(s1's2's3')+b1(s1's2's3)+b2(s1's2s3')+b3(s1's2s3)+

b4(s1s2's3')+b5(s1s2's3)+b6(s1s2s3')+b7(s1s2s3)

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