UNIT 5 COMBINATIONAL LOGIC CIRUIT

How many inputs & outputs does Full Adder Circuit have?

• 2 inputs ; 3 outputs
• 2 inputs ; 2 outputs
• 3 inputs ; 2 outputs
• 3 inputs ; 3 outputs

How many inputs & outputs does Half Adder Circuit have?

• 2 inputs ; 3 outputs
• 2 inputs ; 2 outputs
• 3 inputs ; 2 outputs
• 3 inputs ; 3 outputs

A full adder circuit can be realized using __________.

• One Half Adder & One OR Gate
• Two Half Adders & One OR Gate
• Two Half Adders & Two OR Gates
• One Half Adder & Two OR Gates

A half adder circuit can be realized using __________.

• One EX-OR Gate & One AND Gate
• One EX-OR Gate & One OR Gate
• One EX-NOR Gate & One AND Gate
• One EX-NOR Gate & One OR Gate

A 3-bit parallel adder can add

• three 2-bit binary numbers
• two 3-bit binary numbers
• three bits at a time
• three bits in sequence

Which gate is best used as a basic comparator?

• NOR
• OR
• Exclusive-OR
• AND

If a 74HC85 magnitude comparator has A = 1000 and B = 1010, the outputs are

• A > B = 0; A < B = 0; A = B = 0
• A > B = 0; A < B = 0; A = B = 1
• A > B = 0; A < B = 1; A = B = 0
• A > B = 1; A < B = 0; A = B = 0

If an octal-to-binary priority encoder has its 0, 2, 5, and 6 inputs at the active level, the active-HIGH binary output is

• (110)2
• (010)2
• (101)2
• (000)2

If a 3-to-8 line decoder with active-LOW outputs exhibits a LOW on the decimal 6 output, what are the status of inputs?

• C = 1; B = 0; A = 1
• C = 1; B = 0; A = 0
• C = 1; B = 1; A = 0
• C = 0; B = 1; A = 0

A decoder can be used as a demultiplexer by ________.

• connecting all enable pins to LOW LOGIC
• connecting all data pins to LOW LOGIC
• connecting all data pins to HIGH LOGIC
• using the input lines for data selection and an enable line for data input