Semiconductor & Computer Engineering
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== Basic design == | == Basic design == | ||
| + | <div style="float:right;"> | ||
| + | <math>A + B = Q</math><br /> | ||
| + | <math>0_2 + 0_2 = 00_2</math><br /> | ||
| + | <math>0_2 + 1_2 = 01_2</math><br /> | ||
| + | <math>1_2 + 0_2 = 01_2</math><br /> | ||
| + | <math>1_2 + 1_2 = 10_2</math> | ||
| + | </div> | ||
| + | A 1-bit adder adds two single-bit values together. There are four such possible operations. All but the 1+1 operation result in a single-digit sum. The 1+1 operation produces a sum with two digits. The higher significant bit of that value is known as a carry. The digital component that performs the addition of two bits is called a '''half adder'''. When two multi-bit numbers are added together, the carry out from the lower bit must be accounted for in the higher addition of the higher bits. When a half adder accounts for a carry in, it becomes a '''full adder'''. | ||
| + | |||
| + | == Half Adders (HA) == | ||
| + | {{empty section}} | ||
| + | |||
| + | == Full Adder (FA) == | ||
{{empty section}} | {{empty section}} | ||
Revision as of 05:25, 12 April 2014
An adder (sometimes called a summer) is a digital circuit that adds two N-bit numbers and generates an N-bit number. In addition to generating a sum, adders often also generate an overflow flag and a carry flag. Adders are used in many parts of the microprocessor such as the ALU, PC, counters, calculating effective addresses and table indices, multipliers, filters, and in various other components.
Basic design
A 1-bit adder adds two single-bit values together. There are four such possible operations. All but the 1+1 operation result in a single-digit sum. The 1+1 operation produces a sum with two digits. The higher significant bit of that value is known as a carry. The digital component that performs the addition of two bits is called a half adder. When two multi-bit numbers are added together, the carry out from the lower bit must be accounted for in the higher addition of the higher bits. When a half adder accounts for a carry in, it becomes a full adder.
Half Adders (HA)
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This section is empty; you can help add the missing info by editing this page. |
Full Adder (FA)
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This section is empty; you can help add the missing info by editing this page. |
BCD Adders
- Main article: BCD Adder
Most adders typically use the binary numeral system, however they can use any other numerical representation such as binary-coded decimal. Binary adders are typically simpler to design when compared to a BCD adder where roughly 20 percent more circuitry is required.
Advanced Designs
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This section is empty; you can help add the missing info by editing this page. |