ENT265 Microcontroller & Interfaces

1. ENT265Microcontroller & Interfaces Chapter 0 & 1 Introduction to Computer Architecture 28 Dec 2009

2. Basic Computer Architecture • CPU (Central Processing Unit) • Memory • Input/Output Buses I/O CPU Memory

3. Inside the computer

4. Internal Organization of a Computer

5. CPU Function: To execute (process) information stored in memory • I/O Devices: Communicating with the real world • CPU connected to memory and I/O through strips of wire called bus

6. Microcontroller versus Microprocessor

7. Microprocessor System Contrasted With Microcontroller System

8. Simplified View of a PIC Microcontroller

10. PIC Program ROM • Also known as Code ROM • Used for storing programs. Several versions of ROM: • UV-EPROM • Flash • One-Time-Programmable (OTP)

11. PIC RAM • Space for data storage • Has two component: • General Purpose Register (GPR) • Scratch pad • Special Function Register (SFR) • Module function usage

12. PIC EEPROM (Optional) • To store critical data that does not need to be change very often

13. The CPU • Purpose: The controlling element in a computer system that performs data transfers, integer arithmetic and logic, and input/output operations. • Sizes: 4-bits to 64-bits • Speeds: up to 4 GHz • A byte is 8-bits • Memory is addressed by byte • RISC vs. CISC

14. CPU Task • Executes instructions from the memory system. • A program is a collection of instructions stored sequentially in the memory. • A program is the computer’s software. • The stored program concept makes the computer fast and powerful.

15. Data Transfer Operations • Most of a CPUs time is spent transferring data. • Data transfers include: instruction fetches, transfers between memory and registers, transfers between registers and I/O. • Transfers occur though the data bus.

16. Arithmetic and Logic Operations • The CPU performs arithmetic on integers using addition, subtraction, multiplication, and division (some microcontrollers do not divide). • Logic operations include AND, OR (inclusive and exclusive), NOT, and shift/rotate.

17. Decisions • The CPU makes decisions based upon numeric facts to control the flow of a program. • Zero—Not Zero, Positive—Negative, Carry—No Carry • Decisions modify the flow of a program • Flow control allows tasks to be repeated or skipped.

18. Memory • Memory in a computer system is normally numbered in bytes. • Memory is accessed by bytes using a memory address (address bus) numbered from memory location 00000000. • Memory addresses are expressed in the hexadecimal numbering system (radix 16). • Memory data flow through the data bus.

19. Data Bus • The data bus is 4-, 8-, 16-, 32-, or 64-bits in width in modern computers. • The size of the CPU and its data bus are the same or in some cases the data bus may be twice as wide as the CPU size. • A 16-bit computer has a 16-bit data bus. • The Pentium 4 is a 32-bit computer with a 64-bit data bus.

20. Address Bus • The address bus selects a memory location or an I/O device • The size (number of bits) of the address bus determines the maximum memory size. • An 8-bit address can address 256 bytes of memory (28). • 1K = 1024 and requires a 10-bit address • 1M = 1024 * 1024 and requires a 20-bit address • 1G = 1M * 1024 and requires a 30-bit address • 1T = 1G * 1024 and requires a 40-bit address

21. Control Bus • The control bus controls memory and I/O. • The control bus contains two main signals that originate from the CPU. • The #RD signal causes a read operation. • The #WR signal causes a write operation. • Some CPUs also contain a signal that selects memory or I/O called M/#IO.

22. ROM • A ROM is a nonvolatile memory that is used to store programs and static data • The ROM is usually either an EPROM or an EEPROM memory. • The EPROM is erased using an ultraviolet lamp. • The EEPROM is erased electrically • In either device, memory does not change when power is removed from the system.

23. RAM • The RAM is the read/write memory in a system that stored dynamic data and will not retain data without power. • RAM is available as either SRAM or DRAM. • SRAM stores data as long as power is applied. • DRAM must be refreshed because it only stores data for a few milliseconds. • Large memory system usually use DRAM and small memory systems usually use SRAM.

24. I/O • The I/O in a computer allows the CPU and its program to communicate to humans and machines. • A input device inputs data to the CPU and examples include keyboards and switches. • An output device accepts data from the CPU and examples include printers, indicators, and so forth. • I/O data is often 8-bits in width.

25. Internal Architecture: von-Neumann Architecture The CPU can either read an instruction or read/write data from/to the memory. Both cannot occur at the same time

26. Internal Architecture: Harvard Architecture CPU can read an instruction and perform a data memory access at the same time

27. INSTRUCTION SET RISC (Reduced Instruction Set Computer) i.e. PIC Microcontroller CISC (Complex Instruction Set Computer) i.e. Intel 8085

28. Number Systems • Numbers systems used with computers are usually binary and hexadecimal. • Positional notation is often used to convert a number from any number system to decimal. Power 22 21 20 2-1 2-2 2-3 Weight 4 2 1 .5 .25 .125 Number 1 1 0 . 1 0 1 Numeric Value 4 + 2 + 0 + .5 + 0 + .125 = 6.625

29. Power 161 160 16-1 Weight 16 1 .0625 Number 6 A . C Number Value 96 + 10 + .75 = 106.75

30. The number 764 represented in three different ways

31. The number 218 represented in binary and decimal system

32. Binary and Hexadecimal number

33. Hexadecimal to decimal number conversion

35. Byte: High and Low nibbles

36. Whole Number Conversion from Decimal • The key is division by the radix or number base. • The algorithm: 1. Divide the decimal number by the radix (number base). 2. Save the remainder (first remainder is the least significant digit). 3. Repeat steps 1 and 2 until the quotient is zero.

37. To convert 10 decimal to binary 2) 10 remainder = 0 2) 5 remainder = 1 2) 2 remainder = 0 2) 1 remainder = 1 result = 1010 0

38. To convert 106 decimal to hexadecimal 16) 109 remainder = 13 (D) 16) 6 remainder = 6result = 6D 0

39. Converting fractions from Decimal • The key is multiplication by the radix • The Algorithm 1. Multiply the decimal fraction by the radix (number base). 2. Save the whole number portion of the result (even if zero) as a digit. Note that the first result is written immediately to the right of the radix point. 3. Repeat steps 1 and 2, using the fractional part of step 2 until the fractional part is zero.

40. Converting 0.125 to binary .125 x 2 0.25 digit is 0 .25 x 2 0.5 digit is 0 .5 x 2 1.0 digit is 1 result = 0.0012

41. Converting 0.046875 to hexadecimal .046875 x 16 0.75 digit is 0 .75 x 16 12.0 digit is 12(C) result = 0.0C16

42. Binary Coded Hexadecimal (BCH) • Hexadecimal number are converted to binary in groups of 4-digit binary number by inspection. • For example to convert 2A hexadecimal to binary convert to 2 to 0010 and the A to 1010 as follows: 2A = 0010 1010

43. Binary to BCH 101001001 = 0001 0100 1001 = 1 4 9

44. Complements • Two types of complements exist: The radix complement and the radix minus ones complement. • The radix complement minus 1 is the 1’s complement for binary and is created by subtracting each digit from 1. 1111 1111 – 0100 1100 1011 0011

45. Radix Complement • The radix complement is the two complement in binary and is created by forming the 1’s complement and adding a 1 to the 1’s complement 1111 1111 – 0100 1000 1011 0111 (one’s complement) + 1 1011 1000 (two’s complement)

46. 15 15 15 – 3 4 5 C B A (fifteen’s complement) + 1 C B B (sixteen’s complement)

47. ASCII Data • ASCII (American Standard Code for Information Interchange) is the code most often used for alphanumeric data. • The ASCII code is a 7-bit code and the extended ASCII code is an 8-bit code.

48. Standard ASCII

49. Extended ASCII

50. Storing ASCII Code in an Assembly Language Program DB 'B' DB 'r' DB 'e' DB 'y' DB 0x00 DB 'Brey', 0 DATA "Brey", 0 DATA "Barry", 0