How many 3-to-8 Decoders with enable inputs are needed to construct a 4-to-16 Decoder?
To construct a 4-to-16 decoder, 2 3-to-8 decoders are required. The most significant input bit (A3) acts as the Enable control (using an inverter for one decoder and direct input for the other), while the remaining 3 bits (A2, A1, A0) are connected to both decoders.
In a BCD (Binary Coded Decimal) Adder, what binary correction factor must be added if the 4-bit binary sum exceeds 9 (1001) or produces a carry?
BCD represents digits 0 to 9 using 4 bits. Since 4 bits can represent up to 15 (16 states), the states 10 to 15 (6 invalid states) are skipped. Adding 6 (0110 in binary) skips these invalid states and produces the correct BCD digit and carry.
Which of the following programmable logic devices features a fixed AND array and a programmable OR array?
PROM consists of a fixed AND array (which acts as a full decoder generating all minterms) and a programmable OR array (where minterms are combined).
Which programmable logic device (PLD) architecture consists of a programmable AND array and a fixed OR array?
PAL (Programmable Array Logic) features a programmable AND array and a fixed OR array. This makes PAL easier to manufacture and program compared to PLA.
A 2-bit magnitude comparator compares two 2-bit numbers A = A1 A0 and B = B1 B0. What is the Boolean expression for the equality output (A = B)?
XNOR gate outputs 1 when both input bits are equal. For A = B, corresponding bits must be equal: (A1 XNOR B1) = 1 AND (A0 XNOR B0) = 1. Thus, (A = B) = (A1 ⊙ B1)(A0 ⊙ B0).