M. Amer Iqbal Qureshi
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- Điều hướng trang này:
- EXCLUSIVE OR gate
| OR gate
Similar to the previous case, OR gate also has two or more inputs and one output. The gate with only two inputs will be considered in this case as well. A logic one (1) will appear on its output in case either one or another output (A OR B) is driven to logic one (1). In case the OR gate has more than two inputs, the following applies: a logic one (1) appears on its output in case at least one input is driven to logic one (1). In case all inputs are driven to logic zero (0), the output will be driven to logic zero (0). Not gate This logic gate has only one input and only one output. It operates in an extremely simple way. When logic zero (0) appears on its input, a logic one (1) appears on its output and vice versa. This means that this gate inverts signal by itself and because of that it is sometimes called Fig. 10 Use of Logical AND in Software Fig. 11 The OR Gate with Truth Table Fig. 12 The OR being Used in Software Fig. 13 The NOT Gate Teach Yourself PIC Microcontrollers | www.electronicspk.com | 16 inverter. In a program, logic NOT operation is performed on one byte bits. The result is a byte with inverted bits. If byte bits are considered to be a number, inverted value is actually a complement of that number, i.e. The complement of a number is what is needed to add to it to make it reach the maximal 8 bit value (255). EXCLUSIVE OR gate This gate is a bit complicated comparing to other gates. It represents combination of all previously described gates. It is not simple to define mutual dependence of input and output, but we will anyway try to do it. A logic one (1) appears on its output only in case the inputs have different logic states. In a program, this operation is commonly used to compare two bytes. Subtraction may be used for the same purpose (if the result is 0, bytes are equal). The advantage of this logic operation is that there is no danger Teach Yourself PIC Microcontrollers | www.electronicspk.com | 17 to subtract larger number from smaller one. Register A register or a memory cell is an electronic circuit which can memorize the state of one byte. In other words, what is a byte theoretically, it is a register practically. tải về 3.06 Mb. Chia sẻ với bạn bè của bạn:
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