1. EE 1001 Digital Topics Introduction to Electrical Engineering Dr. Chris Carroll MWAH 252 726-7530 ccarroll

2. Digital Logic Circuits Foundation for digital computer design Basics are easy... Discrete, two-valued variables Finite number of possible functions Complex operations built from easy basics Combinational circuits (no memory) Sequential circuits (memory)

3. Combinational Circuits AND gate Inputs Output 0 0 0 0 1 0 1 0 0 1 1 1 OR gate Inputs Output 0 0 0 0 1 1 1 0 1 1 1 1 XOR gate Inputs Output 0 0 0 0 1 1 1 0 1 1 1 0 NOT gate Input Output 0 1 1 0

4. Sequential Circuits Memory stores “state” of the circuit Implemented with flip-flops Clock signal switches 0  1  0  1  … Flip-flop captures data on clock 0  1 change D flip-flop is one of several kinds available D Q clock

5. Counters Simplest kind of sequential circuit “Count” advances once per clock 0  1 Count sequence determined by circuit Sequence advances unconditionally every time the clock goes 0  1 Flip-flops store the “state” of the circuit

6. Binary UP-counter Now Next Q L Q R Q L Q R 0 0 0 1 0 1 1 0 1 0 1 1 1 1 0 0 D Q L clock D Q R clock

7. Binary DOWN-counter Now Next Q L Q R 0 0 1 1 1 1 1 0 1 0 0 1 0 1 0 0 D Q L clock D Q R clock

8. Gray-Code Counter Now Next Q L Q R Q L Q R 0 0 0 1 0 1 1 1 1 1 1 0 1 0 0 0 D Q L clock D Q R clock

9. 3-State, Self-Starting Now Next Q L Q R 0 0 0 1 0 1 1 0 1 0 0 0 1 1 1 0 D Q L clock D Q R clock

10. Computer Architecture How to build a computer Many philosophies Complex Instruction Set Computer (CISC) Reduced Instruction Set Computer (RISC) Always three parts of any computer Central Processing Unit (CPU) Memory (for both program and data) Input/Output (I/O)

11. Microprocessors CPU portion of a computer on a chip Requires external memory and I/O Examples: 4004 (first microprocessor, 4-bit) 8080 (popular 8-bit) 8086 (16-bit, early PC’s used this) Pentium (32-bit, 64-bit) Others…

12. Microcontrollers Entire computer on a chip Central Processing Unit (CPU) Memory Input/Output (I/O) Easy to embed in larger systems Modern cars include 10’s of these

13. Hexadecimal (base sixteen!) Uses sixteen digits, 0-9 and a-f a=10, b=11, c=12, d=13, e=14, f=15 XY 16 = X * 16 + Y Or, in binary… 0000 2 = 00100 2 = 41000 2 = 81100 2 = c 0001 2 = 10101 2 = 51001 2 = 91101 2 = d 0010 2 = 20110 2 = 61010 2 = a1110 2 = e 0011 2 = 30111 2 = 71011 2 = b1111 2 = f

14. Advantage of hexadecimal? Easy conversion binary ↔ hexadecimal Each 4-bits of binary is 1 hex digit 10010110 2 = 96 16 11010010 2 = d2 16 8a 16 = 10001010 2 c3 16 = 11000011 2

15. Summary Digital is everywhere! Even analog things can be digitized Complexity is manageable High performance, low cost