Logic diagrams starter teacher version
- 1. O = NOT (A AND B) O = NOT (A OR B) O = (NOT A) AND B Make a TRUTH TABLE for each of the above logic diagrams
- 2. Answers NAND NOR
- 3. More about logic tables • To produce a truth table from a logic diagram you need to work out the outputs for every possible combination of inputs. – If a logic diagram has only 2 inputs then there will only be 4 input combinations (00, 01, 10 and 11). – If there are 3 inputs then there will be 8 possible combinations. – 4 inputs would give 16 combinations. • Therefore n inputs gives 2n outputs
- 4. Now try making a TRUTH TABLE for this diagram… This is called a half-adder circuit. Can you work out why?
- 5. Half-adder Circuit • Are designed to add 2 binary numbers with a carry (C) if the sum (S) is greater than 1. • So this can be expressed as a logic statement: S = (A OR B) AND (NOT (A AND B)) C = (A AND B)