Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
Paper format. National Exams, May 2016 — 07-Elec-A4 Digital Systems & Computers. Three hours, closed book, one approved Casio or Sharp calculator. Six questions, each worth 12 points; five questions constitute a complete exam. A flip-flop excitation table and a list of Boolean identities are printed on the last page. Every one of the six questions is solved below, because the set is intended as a study resource rather than an exam script.
Reference texts. M. Morris Mano & M. D. Ciletti, Digital Design (6th ed.), ch. 3 (map simplification, prime implicants, hazards), ch. 5–6 (sequential logic, counters); J. F. Wakerly, Digital Design: Principles and Practices (5th ed.), §3.7 (three-state outputs), §4.4 (timing hazards and consensus terms), ch. 8 (counters); C. Hamacher, Z. Vranesic, S. Zaky & N. Manjikian, Computer Organization and Embedded Systems (6th ed.), ch. 1–2 (processor structure, registers), ch. 3 (memory-mapped I/O).
Check: segment-to-pin assignment in Question 6. Figure 6.1 shows the buffer chip driving the eight segment lines a…h from Port B pins PB7–PB0, but does not print which pin drives which segment. Throughout Question 6 the conventional weighting a = PB0, b = PB1, …, g = PB6, h = PB7 (decimal point) is assumed and stated explicitly, exactly as the paper's own rubric invites ("the candidate is urged to submit…a clear statement of any assumptions made"). Every bit pattern below is derived from that one assumption; a different pin order permutes the bits but changes no part of the method.
