Govt. Exams
Entrance Exams
Mealy machine output depends on both present state and present input. Moore machine output depends only on present state. Mealy machines are more efficient.
An n-bit counter has 2^n possible states (from 0 to 2^n - 1). For 3-bit counter: states are 0 to 7 (000 to 111).
In synchronous counters, all flip-flops change simultaneously, so maximum frequency is determined by one flip-flop delay. f_max = 1/t_pd = 1/10ns = 100 MHz.
A 4-variable K-map has 2^4 = 16 cells, each representing one minterm. To cover all minterms, minimum 16 cells are needed.
In a 4-bit binary counter, states cycle from 0000 to 1111 (0 to 15). After 1111, it wraps around to 0000 (overflow occurs).
Majority function outputs 1 when majority (2 or more) inputs are 1. Expression: AB + BC + AC covers all cases where at least 2 inputs are 1.
Hamming distance = number of positions where bits differ. 1011101 vs 1001001: positions 3, 5, 6 differ. Hamming distance = 3.
Using Boolean algebra: A + AB + ABC = A(1 + B + BC) = A(1) = A. The dominant term A absorbs all other terms.
A combinational circuit can be completely defined using truth table, Boolean expressions, or logic diagram. All three are equivalent representations.
XOR gate has 2 ones in output (when inputs are different). OR has 3 ones. AND has 1 one. These are odd. XNOR has 2 ones (even). XOR is most commonly cited.
