Question

Referring to the circuit in Figure 2 and the corresponding function table in Table 5 on page 5, answer the following questions: a) Draw the state diagram of the circuit (b) (5 Marks) Work out the logic circuit for the Output Block using only NAND gates and inverters. (5 Marks) (c) Give a brief description on the functional characteristics of the circuit in Figure 2 (2 Marks) (d) Redesign the circuit using only one flip-flop and some logic gates. You need to show only the Boolean equation of the decoding logic. (i) One D flip-flop plus logic gates ii) One T flip-flop plus logic gates. 8 Marks) QD Output Block QT CLK- Figure 2

Answer 1

P_t + 1 = F x^bar p_t + xp_t^bar + F_x^bar p_t + 1 = F x^bar p_t + x p_t^bar + F^bar x = F x^bar p_t + x(p_t^bar + F^bar) = x^bar F p_t + x(F^bar p_t^bar) = x^bar y + x y^bar [because Let y = F p_t] (c) In Figure 2, Two flipflops are used. One is D filpflop, where characteristic equation is, Q_DH = D. Another flipflop is T - flipflop, whose characteristic equation is, Q_T + 1 = T exclus Q_T synchronous clock is applied for both the flipflops output block will generate an output of p_t + 1 = F x^bar p_t + x p_t^bar + F^bar x, depending on & different input and state combinations. \r\n (d) (e) Table: - T flip flop excitation table D flip flop Excitation table