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by: Sam Robel


Sam Robel
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Class Notes
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This 14 page Class Notes was uploaded by Sam Robel on Monday October 19, 2015. The Class Notes belongs to ECE 473 at Oregon State University taught by Staff in Fall. Since its upload, it has received 49 views. For similar materials see /class/224428/ece-473-oregon-state-university in Engineering Electrical & Compu at Oregon State University.

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Date Created: 10/19/15
Introduction to Microcontrollers ECE473573 N croprocessor System Design Dr Shiue Introduction It is hard to imagine the present world of electronic devices without the m1croprocessor Cash register scales ovens washing machine alarm clock thermostats and ignition system etc o 1971 Microprocessors Intel 8080 Motorola 6800 RCA 1801 MOS Technology and Zilog Z80 1976 Microcontrollers Intel 8748 MCS 48 family 25 17000 transistors 0 CPU 1KB EPROM 64B RAM 27 IO pins and an 8bit timer 0 Used in washing machines and traffic light controllers 1980 Microcontrollers Intel 8051 MCS51 family 25 60000 transistors CPU 4KB ROM 128B RAM 32 IO Pins a serial port two 16bit timers Siemens SAB80515 68pin parade with siX 8bit IO ports 13 interrupt sources and an 8bit AD converter with 8 input channels ECE473573 2 lVIicroprocessor System Design Dr Shiue A Computer System Computer is de ned by two key traits The ability to be programmed to operate on data without human 1ntervent10n The ability to store and retrieve data More generally a computer system includes Peripheral devices for communicating with the human hardware Program that process data software A Computer system contains Central process unit CPU connected to random access memory RAM and readonly memory ROM via the address bus data M and control bus Interface circuits connect the system buses to peripheral devices see next slide ECE473573 lVlicroprocessor System Design Dr Shiue Block Diagram of A Microcomputer System RAM Interface Peripheral Circuitry H devices CPU 25 fetching instructions and executing instructions 0 Instruction Set Add subtract multiply divide AND OR NOT data movement branch operations as represented by a set of binary codes called the Instruction Set ECE473573 4 lVIicroprocessor System Design Dr Shiue The Central Processing Unit CPU control unit CPU Instruction Program Register counter PC 1R Instruction RegiSterS decode and Register for the temporary storage of information M for performing operations on this information Instruction decode and control m that determine the operation to perform 3 holds the binary code for each instruction as it is executed Arithmetic E holds the memory address of and IOgIC the next instruction to be unlt ALU executed ECE473573 5 lVIicroprocessor System Design Dr Shiue Fetching and Executing the Instructions Executing Steps Decoding the opcode and generating control signals to gate internal registers in and out the ALU and to signal ALU to perform the speci ed operation IR 3 Clock RAM Opcode N READ 4 Fetching Steps 1 The contents of PC are placed on the address bus A READ control signal is activated Data the instruction opcode are read from RAM and placed on data bus The opcode is latched into the CPU s IR 5 The PC is incremented to prepare for the next fetch from memory ECE473573 lVlicroprocessor System Design Dr Shiue RAM and ROM RAM is readwrite memory It is volatile the contents are lost when power is removedUser program and data are loaded into RAM for execution ROM is readonly memory It is nonvolatile ROM is used to hold the short frequently used software routines that perform inputoutput operations ECE473573 7 lVlicroprocessor System Design Dr Shiue The Buses Address Data Control Address Bus 16bit address can access 216 65536 locations 216 26210 64K locations The address bus is unidirctional Data Bus Evidently computers spend up to 23 of their time simply moving data Since the majority of move operations are between a CPU register and external RAM or ROM the number of lines width of the data bus is important for overall performance 16bit computer refers to a computer with 16 lines on its data bus The overall computing power increasing as the width of the data bus increases The limitation bywidth is bottleneck The data bus is bidirectional Read or Write 0 Control Bus Contol signals are timing signals supplied by CPU to synchronize the movement of the information on the address bus and data bus Such as CLOCK READ and WRITE ECE473573 lVlicroprocessor System Design Dr Shiue IO Devices Mass storage devices Online storage is available to CPU without human intervention upon the request of a program such as magnetic disk Archival storage Holds data that are rarely needed and require manual loading onto the system such as magnetic tapes or disks optical discs CDROM Human interface devices Keyboard mouse Printer CRT Controlmonitor devices Temperature control of a building home security elevator control home appliance control The hardware and software interfacing of these devices to microcontroller is one of the main themes in this book ECE473573 lVlicroprocessor System Design Dr Shiue Hardware vs Software Whereas the early days of computing witnessed the materials manufacturing and maintenance costs of computer hardware far surprising the software costs Today with the massproduced LSI LargeScale Integrated chips Hardware costs are less dominant It is the laborintensive job of writing documenting maintaining updating and distributing software that constitutes the bulk of the expense in automating a process using computers ECE473573 lO N croprocessor System Design Dr Shiue Three Levels of Software Inputoutput subroutines Directly manipulate the hardware of the system 0 Reading characters from the keyboard 0 Writing characters to the CRT Reading blocks of information from the disk Since these subroutines are so intimately linked to the hardware they are written by the hardware designers and are stored in ROM They are the BIOS basic inputoutput system on the IBM PC for example 0 The operating system Is a large collection of programs that come with the computer system and provide the mechanism to access manage and effectively utilize the computer s resources These abilities exists through the operating system s command language and utility programs which in turn facilitate the development of application software 0 Application software user interface ECE473573 l l lVlicroprocessor System Design Dr Shiue Microprocessors vs Microcontroller Hardware architecture Whereas a microprocessor is a singlechip CPU a microcontroller contains a CPU and much of the remaining circuitry of a complete microcomputer system in a single IC Microcontrollers as control oriented devices are called upon to response to extemal stimuli in real time They must perform fast context switching suspending one process While executing another in response to an event opening the oven s door Applications Microcontrollers are suitable to control of IO devices in designs requiring a minimum component count Whereas microprocessors are suitable to processing information in computer systems ECE473573 12 lVlicroprocessor System Design Dr Shiue Microprocessors vs Microcontroller Instruction set features Microprocessor instruction sets are processing intensive implying they have powerful addressing modes With instructions catering to operations on large volumes of data Microcontrollers on the other hand have instruction sets catering to the control of inputs and outputs Microcontrollers have builtin circuitry and instructions for inputoutput operations event timing and enabling and setting priority levels for interrupts caused by external stimuli Microprocessors often require additional circuitry serial interface Ics interrupt controllers timers etc to perform similar operations A tight encoding scheme for the instruction set is essential for microcontrollers This is rarely a feature of microprocessors their powerful address modes bring With them a lessthancompact encoding of instructions ECE473573 l3 N croprocessor System Design Dr Shiue New Concepts Consider an examples microwave ovens programmable thermostats electronic scales and even cars The electronics within each of these products typically incorporates a microcontroller interfacing to push buttons switches lights and alarms on a front panel Computer systems have a high RAMtoROM ratio with user programs executing in a relatively large RAM space and hardware interfacing routines executing in a small ROM space Microcontrollers on the other hand have a high ROMto RAM ratio The control program is stored in ROM while RAM is used only for temporary storage ECE473573 l4 N croprocessor System Design Dr Shiue


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