Digital Electronics Unit 2

Unit 2

What is the max no of bits that can be stored in a number

2^n-1

Draw the circuit for a half-adder

Draw the circuit for a full-adder

What is a ripple-carry adder

Multiple full adders put together in parallel

Define an ‘ALU’ (Arithmetic Logic Unit)

A combinational logic circuit that performs logical and shift operations

How many operations can you choose from in an ALU

2^n (n being the no of control bits)

What are bit-wise operations

Where logical operations are done on each pair of individual bits

What’s the purpose of a negation

How do you subtract 2 binary numbers A & B

convert the 2nd number (B) to 2s complement, then add it to A

Define ‘Bit Slicing’

Where circuits of the same bit are combined many times to make a full ALU

Draw the circuit for a ‘Logic Unit’

Draw the circuit for an ‘Arithmetic Unit’

What 2 things do carry-outs apply to

• Unsigned numbers

• Arithmetic operations

What 2 things do overflows apply to

• Signed numbers

• Arithmetic operations

Define ‘Sequential Logic’

Circuits where the current output depends on the current & previous inputs and outputs

Flip-Flops are bi-vibrational, what is meant by this?

They have 2 stable statews

Draw a D-Latch

What happens when E = 0 in a D-Latch

The latch is disabled