Introduction to Microprocessor Systems

1. Introduction to Microprocessor Systems ECE511: Microprocessor & Digital System

2. What we are going to learn in this session: • What is a microprocessor system. • History of microprocessors. • Components inside the microprocessor system: • Component description. • Function. • Arrangement. • The CPU execution cycle. • What is it. • How the cycle works.

3. Introduction • µP is a complex, powerful device: • Able to process huge amounts of data. • Built using transistors on silicon die. • Needs external components to support operation. • Used in wide variety of applications. • Take advantage of processing power. • Microcomputer system – support µP operations.

4. History of Computers

5. History of Computers • Has undergone significant improvements: • 4 generations until now. • Tied to development of electronics, semiconductors. • What’s next? • Conventional computing: • Advancements in semiconductor technology. • Smaller, faster, less power. • Unconventional computing: • Quantum computer. • Chemical computer. • Molecular computer.

6. History of Computers G1 G2 G3 G4 Vacuum Tube Transistor IC Better IC technology

7. History of Computers • First Generation (1954-56): • Vacuum Tubes as switches. • Magnetic drums as memory. • Very big, unreliable, slow. • ENIAC (Electronic Numerical Integrator And Computer ), UNIVAC (UNIVersal Automatic Computer ).

8. First Generation Computers Vacuum Tubes Electronic Numerical Integrator and Computer (ENIAC)

9. History of Computers • Second Generation (1956-63): • After invention of transistors. • Smaller, faster, cheaper. • Limited to military and business use.

10. Second Generation Computers Vacuum tube circuit Transistor circuit

11. History of Microprocessors • Third Generation (1964-71): • After invention of Integrated Circuits (IC). • Many transistors can be packed into IC. • Intel 8008, Intel 4004. • Medium Scale Integration (MSI) and Large Scale Integration (LSI).

12. Early Intel Microprocessors

13. Third Generation Computers PC Laptop

14. History of Computers • Fourth Generation (1971-now): • Improvements in IC technology, µP design. • More transistors  more processing power. • Very Large Scale Integration (VLSI). • Intel Montecito Itanium: 1 bln. transistors. • Reduced Instruction Set Computers (RISC). • 64-Bit microprocessors.

15. Fourth Generation Computers

16. Comparison Computer Speed Memory Cost UNIVAC (1st Gen.) $1.6 million 1.3 kHz 1MB IBM 1401 (2nd Gen.) $47,900 2.2 kHz 1.4kB DEC PDP-8 (3nd Gen.) $20,000 1 MHz 6 kB $700 Pentium III (4th Gen.) 500 MHz 128 MB

17. Microprocessor Systems

18. Microprocessor Systems • Complete system built around microprocessor. • CPU. • Memory. • I/O: disk drives, keyboard, mouse. • System Bus. • Supporting circuitry. • CPU as the “brain” – controls actions of all components.

19. Microprocessor System - PC ROM Floppy RAM CPU CD-ROM Supporting Circuitry Keyboard Mouse HDD

20. Microprocessor System - Calculator Memory CPU Power Supply LCD Display Keypad

21. Computer Interface

22. Computer Interface • A µP-based system consists of many components: • CPU. • Memory. • I/O: disk drives, keyboard, mouse. • System Bus. • Supporting circuitry. • All components communicate using System Bus.

23. Block Diagram Parallel I/O Serial I/O Interrupt Circuit System Bus Timing CPU Memory

24. The CPU CPU • “Master” of all components. • Job: • Get instructions from memory. • Execute instructions. • Perform calculations (Co-processor). • Control bus operations.

25. The CPU • CPU consists of: • ALU (Arithmetic/Logic Unit): • Performs arithmetic/ logic computations. • CU (Control Unit): • Responsible to retrieve instructions, analyze, then execute. • Registers: • Fast internal storage • Used to temporarily store addresses, data, processor status.

26. System Bus • Communication “highway” for all components. • Contains: • Data lines. • Address lines. • Control lines: regulate information transfer, interrupts, error signals.

27. Memory Memory • Stores instructions and data for CPU. • Each memory location given unique address. • CPU refers to address to access. • Types: • Read-Only Memory (ROM). • Random-Access Memory (RAM). • Non-Volatile Memory (NVM).

28. RAM, ROM and NVM ROM Stores start-up instructions and critical system data and variables. Memory NVM RAM Stores general data and applications

29. ROM • Read-Only Memory: • Data can be read, but cannot be written (read-only). • Contents stay without power (non-volatile). • Usually contains basic start-up instructions, data. • Contents hard-wired during manufacturing. • Newer versions can be reprogrammed: • PROM: Fuse & anti-fuse. • EPROM: UV light. • EEPROM: Electrical current.

30. ROM Examples EEPROM Programmer EPROM Quartz Window

31. NVM • Non-Volatile Memory • Contents can be read and written. • Contents stay without power (non-volatile). • Advantages: • Keeps memory even with no power. • Data is protected against blackouts. • Rewriteable. • Disadvantages: • Slower than RAM.

32. RAM • Random Access Memory. • Contents can be read and written. • Loses data without electrical power (volatile). • Advantages: • Programs can be loaded and reloaded. • Larger capacity. • Disadvantages: • Requires power, refresh cycles.

33. RAM vs. ROM RAM is still empty because the computer has just been started. Computer is turned on CPU looks for instructions from memory CPU loads instructions from ROM.

34. RAM vs. ROM RAM loads more advanced functions, such as the OS. ROM only has basic functions to start the computer.

35. Timing Circuit Timing • Synchronizes all components in the system. • All components refer to the clock timing for operations. • Generates square waves at constant intervals. • Crystal oscillator + timing circuitry. • Higher clock speed allow computers to function faster.

36. Crystal Oscillator Symbol Equivalent Circuit Sample

37. T T T Clock Signal

38. Clock Signal vs. Processing Speed • Instruction CLR.W D7 takes 4 cycles to complete. Slow clock speed time Fast clock speed

39. I/O • Input/Output. • Connects µP with external devices: • Add functionality to µP. • Interfaces with µP using ports. • Examples: • Keyboard. • Mouse. • Display monitor.

40. How do ports connect to system bus? Built into board Using card slots.

41. Serial I/O Serial I/O • Sends/receives data sequentially across 2 channels. • One for receive, one for transmit. • Connects using serial ports. • Advantages: • Less crosstalk. • Disadvantages: • Slow. • Needs special circuit to convert back to parallel (UART – Universal Asynchronous Receiver/Transmitter).

42. Serial Port

43. Parallel I/O Parallel I/O • Sends/receives data across multiple lines at one time. • Connects using parallel ports. • Advantages: • Faster than serial. • Simpler circuits – doesn’t need UART. • Disadvantages: • Crosstalk.

44. Parallel Port

45. 1011011010101010011010101010100011101100101 1011011010101010011010101010100011101100101 1011011010101010011010101010100011101100101 1011011010101010011010101010100011101100101 1011011010101010011010101010100011101100101 Parallel vs. Serial I/O Receive Transmit Serial Port Receive/Transmit Receive/Transmit Receive/Transmit . . Parallel Port

46. UART UART 1 0 From Device To System Bus 1001 0 1 UART 1 0 To Device From System Bus 1001 0 1

47. Interrupt Circuit Interrupt Circuit • Allows other components to “interrupt” normal CPU operation: • Prioritize CPU tasks. • Error detection mechanism. • Accept inputs from devices – keystroke, mouse press. • Depends on task importance: • Important tasks given higher interrupts. • Less important tasks queued. • CPU keeps track of current interrupt level.

48. CPU Device • CPU is performing • tasks normally. 2. Device has more important task that requires immediate attention. 4. CPU saves its current task so that it can return to it when the interrupt completes. 3. Device requests interrupt from CPU. 5. CPU services the interrupt. 6. CPU reloads saved task, and resumes normally. How Interrupts Work

49. Watchdog Monitor • Watchdog monitor: • Special circuit - monitors the system for errors. • Informs the CPU. • CPU takes appropriate actions – reset system, halt processor. • May work in two ways: • Constantly monitor the system, and sends signal if error detected. • Continuously sending signal to CPU after certain interval: • If CPU receives signal, continues processing. • If CPU doesn’t receive signal, something’s wrong.

50. How Watchdogs Work CPU Watchdog • CPU is performing • tasks normally. 1. Watchdog monitors bus for errors. 3. CPU saves its current task so that it can return to it when error is resolved. 2. If error detected, inform CPU. 4. CPU fixes the error. 5. CPU reloads saved task, and resumes normally. 5. If error is too serious, CPU may reset/halt system.