+A traffic light control at a simple intersection uses a binary counter to produ
ID: 671337 • Letter: #
Question
+A traffic light control at a simple intersection uses a binary counter to
produce the following sequence of combinations on lines A, B, C, and D: 0000,
0001, 0011, 0010, 0110, 0111, 0101, 0100, 1100, 1101, 1111, 1110, 1010, 1011,
1001, 1000. After 1000, the sequence repeats, beginning again with 0000,
forever. Each combination is present for 5 seconds before the next one
appears. These lines drive combinational logic with outputs to lamps RNS
(red—north/south), YNS (yellow—north/south), GNS (green—north/south),
REW (red—east/west), YEW (yellow—east/west), and GEW (green—east/
west). The lamp controlled by each output is ON for a 1 applied and OFF for a
0 applied. For a given direction, assume that green is on for 30 seconds, yellow
for 5 seconds, and red for 45 seconds. (The red intervals overlap for 5 seconds.)
Divide the 80 seconds available for the cycle through the 16 combinations into
16 intervals and determine which lamps should be lit in each interval based on
expected driver behavior. Assume that, for interval 0000, a change has just
occurred and that GNS = 1, REW = 1, and all other outputs are 0. Design
the logic to produce the six outputs using AND and OR gates and inverters
Explanation / Answer
according to the meaning of the questions:
1. The first set up a group of four bits binary counter
counter clock signal cycle is five seconds
2. The output from the counter to the combinational logic combined into
fact, this is a binary code switch Ge Gray code
3. group synthesized logic "East and West" - "red yellow and green," a total of six lights, including:
red - red with a set of overlapping time to arrange after the yellow light is reasonable
when DCBA = 000 When the "north-south green" + "something red"
problem solving:
1. Take a cycle is five seconds of the clock signal
2. Design fourteen yuan counter (ZYXW)
3. Solution according to the truth table of the combinational logic (ZYXW) => ( DCBA)
4. Solution according to the truth table of the combinational logic (DCBA) => six LED output
truth table as follows:
---- ---- ------ ------
counter combinations north-south thing
ZYXW DCBA red yellow red yellow
---- => ---- => ------------
00000000001100
00010001001100
0010001100 1100
00110010001100
01000110001100
01010111001100
01100101010100
01110100100100
100011001000 01
10011101100001
10101111100001
10111110100001
11001010100001
11011011100001
11101001100010
11111000100100
---- ---- ------ ------
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