Logic gates
- Basic Logic gates:
- NOT, AND, OR, NOR, NAND, XOR
- Within them, NAND and NOR are said to be universal
- with NAND / NOR you can build any other gates
Exercise: With NAND gate only, build NOR gate
In ICs (CPU, RAM etc)
- The circuit is most likely build with NAND gates only
- NAND gates have better performance than NOR
- Keeping all building blocks in IC (Integrated circuit) the same so the cost will be cheaper / easier to manufacturer
Flip-flops
SR/JK flip-flop
- Sometimes it's called a 'latch'
- A sequential circuit which output depends on the input and previous output
Simplifying Circuit using Boolean Expression
- Write Circuit in Boolean Expression
- Simplify the Expression
- Redraw the simplified circuit
- Verify in Truth Table
Simplify the followings
\overline{(\bar A.\bar B)}
A.B + A.\bar B
A.(B+1)
\overline{A.B} + \overline{(A+\bar B)}
(X+Y).(X+\bar Y)
\overline{\bar A + \overline{(B.A)}}
A.B.\bar C+A.\bar C
B.(A+\bar A)
A.B + B
\bar B.\overline{\bar A+\bar B}
(B+AC).(B+\bar A)
(B+A\bar B).(C+AC)
[CSAL] Boolean Algebra and Logic Circuits
By Andy tsui
