Carryout bit? Carryout bit is ‘1’ also on four cases. When a, b and carryin are 110, 101, 011, 111. Does it mean that we need a similar circuit as sum?

Carryout bit Actually, it can be simpler

Delay Hardware has delays. Delay is defined as the time since the input is stable to the time when the output is stable. How much delay do you think the one-bit half adder is and the one-bit full adder is?

7/6/2019 1-Bit Adder CDA3100 week09-1.ppt

32-bit adder How to get the 32-bit adder used in MIPS?

32-bit adder

Examples Ex 1. Assume that X consists of 3 bits, x2 x1 x0. Write a logic functions that is true if and only if X contains only one 0

EX 1 X2 X1 X0 output 1

EX 1 X2 X1 X0 output 1

Ex 1 Output = x2x1x0’ + x2x1’x0 + x2’x1x0

Ex 2 Assume that X consists of 3 bits, x2 x1 x0. Write a logic functions that is true if and only if X contains an even number of 0s

EX 2 X2 X1 X0 output 1

EX 2 X2 X1 X0 output 1

Ex 2 Output = x2x1’x0’ + x2’x1’x0 + x2’x1x0’+ x2x1x0

Ex 3 Assume that X consists of 3 bits, x2 x1 x0. Write a logic functions that is true if and only if X when interpreted as an unsigned binary number is no less than 5.

Ex 3 X2 X1 X0 output 1

Ex 3 X2 X1 X0 output 1

Ex 3 Output = x2x1’x0 + x2x1x0’+ x2x1x0

Examples Assume that X consists of 3 bits, x2 x1 x0. Write a logic functions that is true if and only if X when interpreted as an unsigned binary number is less than 4.

Some Problems Implement a circuit with three inputs (X2, X1, X0), and one output O. O should be 1 only when X2, X1, X0 are representing an odd binary number.