Книга: Introduction to Microprocessors and Microcontrollers
The OR gate
The OR gate
This follows on nicely from the AND gate. The OR gate gives a logic one at its output if either (or both) of the inputs is at a logic one. Just like the AND gate, the OR gate can have as many inputs as we wish but in a microprocessor, we only use two input versions. Its symbols and truth table are shown in Figures 5.8 and 5.9.
Figure 5.8 Symbols for an OR gate
Figure 5.9 The truth table for an OR gate
Another extra bit
The OR function can be written as + or sometimes ?. So, if an OR gate had two inputs called A and B and an output called X, then we could write X=A+B or X=A?B. Don’t mistake this + sign as ‘plus’ as in addition 3+4=7.
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