Digital Logic Design Questions & Answers

Digital Logic Design Questions & Answers A logic designer needs an INVERTER, and all that is available is one XOR gate from a 74HC86 chip. Does he need another chip? - CORRECT ANSWER- 3. No; the available XOR gate can be used as an INVERTER by connecting one of its inputs to a constant HIGH (see Example 4- 16). Change each AND gate in Figure 4-1(a) to a NAND gate. Determine the new expression for x and simplify it. - CORRECT ANSWER- x=A+B+C^lineAll Define hierarchical design. - CORRECT ANSWER- See glossary. Design a circuit to pass signal A only when B is HIGH and C is LOW. The output must be LOW when A is not being passed. - CORRECT ANSWER- x=ABC^ Design a logic circuit with three inputs A, B, C and an output that goes LOW only when A is HIGH while B and C are different. - CORRECT ANSWER- x=A(B++C)^lineAll How are truth tables implemented in AHDL? - CORRECT ANSWER- Using the keyword TABLE How are truth tables implemented in VHDL? - CORRECT ANSWER- Using selected signal assignments How does a CMOS integrated circuit respond to a floating input? - CORRECT ANSWER- 0 to 1.5 V; 3.5 to 5.0 V How does a TTL integrated circuit respond to a floating input? - CORRECT ANSWER- 0 to 0.8 V; 2.0 to 5.0 V How many XOR gates are required to check the parity bit for an eight-bit data value (plus one parity bit)? - CORRECT ANSWER- eight