CSE 120 Lecture Notes - Lecture 9: Subtraction, Digital Electronics, Logic Gate
9 May 2018
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CSE 120 Lecture Nine Notes - Adders & Subtracters, Gate Delays
Adders
● Digital circuit that performs addition of numbers
● Used in arithmetic logic units
● Also used to calculate addresses, table indices, increment and decrement operators,
and similar operators
● Different types of Adders
○ Half Adder
○ Full Adder
○ Multi-Bit Adder
● Utilizes Truth Tables
Subtracters
● Designed with same approach as an adder
● Three bits involved in the subtracter
○ Input
■ Minuend
■ Subtrahend
■ Bit order position
● 𝑋𝑖− 𝑌
𝑖 − 𝐵𝑖
○ Output
■ Difference Bit
■ Borrow Bit
● Example basic subtractor equation
○ -B = 𝐵+1
○ A - B = A + (-B)
○ = A + 𝐵+1
● Half Subtractor
