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sol2_05

# sol2_05 - 05-1 D Latch(15 a Use only 4 NOR gates and...

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ELEC151 Mid-term Exam. #2, 1/8 05-1. D Latch (15%) a). Use only 4 NOR gates and necessary inverters to design a negative level- sensitive D latch. (5%) b). Use only 2 transmission gates and necessary inverters to design a positive level- sensitive D latch. (5%) c). Use only 1 transmission gate, 1 tri-state inverter and necessary inverters to design a positive level-sensitive D latch. (5%) (Hint: use the tri-state inverter to replace one transmission gate and one inverter in (b).) The positive and negative level-sensitive D latches can be represented by the following symbols, respectively. a) Replace NAND gates of D-latch in Figure 5-6 of textbook by NOR gates. The D- latch of by NAND gates is positive level sensitive, The D-latch by NOR gates as below is negative level sensitive. b) Refer to lecture note 5-37 c) Refer to the solution of past paper 2002-3C. The master latch was a D latch made by one tri-state inverter, one transmission gate and necessary inverters. D Q CLK D Q CLK Q’ Q D CLK D CLK Q Q’ CLK D Q Q’ ELEC151 Mid-term Exam. #2, 2/8 05-2 Shift Register (20%) The logic diagram of an electronic lamp handball is shown below. The ball is simulated by a moving light that is shifted left or right through the bidirectional shift registers. The functional table the 74194 shift register is available on the next page. (a) The circuit is first initialized with the Reset switch. What happens to the Shift registers after the player presses the Reset switch? (4%) (b) During the game, what is the position of the Reseat switch? Open or close? (2%) (Note that the input is treated as logic 1 if it is open in TTL IC.) (c) After the circuit is initiated, what happens if the player presses the Start switch?

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sol2_05 - 05-1 D Latch(15 a Use only 4 NOR gates and...

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