1. 3.1 Logic Signals and Gates Logic Signals ReturnNext  Logic Value: Many physical quantities can be represented two possible numbers or logic values — 0 and 1 (See P81 Table 3- 1). A logic value is often called a binary digit, or bit.  LOW and HIGH: LOW: A signal in the range of algebraically lower voltages.

2. 3.1 Logic Signals and Gates  Positive Logic and Negative Logic NextBack High: A signal in the range of algebraically higher voltages. t v VHVH VLVL Positive Logic 1 0 t v VHVH VLVL Negative Logic 1 0 Return

3. 3.1 Logic Signals and Gates Gates and Truth Tables  AND gate X Y F XYF 00110011 01010101 00010001 Truth table for an AND gate with two inputs  An AND gate produces a 1 output if and only if all of its inputs are 1; and produces a 0 output if any input is 0. F=XY NextBackReturn

4. 3.1 Logic Signals and Gates  OR gate XYF 00110011 01010101 01110111 Truth table for an OR gate with two inputs  An OR gate produces a 1 output if any input is 1; and produces a 0 output if and only if all of its inputs are 0. F=X+Y X Y F NextBackReturn

5. 3.1 Logic Signals and Gates  NOT gate XF 0101 1010 Truth table for a NOT gate  A NOT gate, usually called an inverter, produces an output value that is the opposite of its input value. X F NextBackReturn

6. 3.1 Logic Signals and Gates  NAND gate Truth table for a NAND gate NextBackReturn X Y F XYF 00110011 01010101 11101110  A NAND gate produces a 0 output if and only if all of its inputs are 1; and produces a 1 output if any input is 0.

7. 3.1 Logic Signals and Gates  NOR gate Truth table for a NOR gate BackReturn XYF 00110011 01010101 10001000  A NOR gate produces a 1 output if and only if all of its inputs are 0; and produces a 0 output if any input is 1. X Y F