me 515 mechatronics - faculty of...

ME 201 Mechanics of Machines 1/2/2007

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ME 515 Mechatronics

Microcontroller Based Control of Mechanical Systems

Asanga RatnaweeraDepartment of Mechanical Engineering

Faculty of Engineering University of Peradeniya

Tel: 081239 (3627)Email: [email protected]

2 January 2007 Asanga Ratnaweera, Department of Mechanical Engineering

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A microprocessorPerforms arithmetic and logic operations

Receives digital input process according to stored program (variable) digital output

Two main parts: arithmetic unit (AU) control unit (CU)


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A microprocessorArithmetic unit made up of:

Arithmetic Logic Unit (ALU)arithmetic calculations + logic operations

Accumulators (ACC) where arithmetic calculations are made

Condition Code Register (CCR) set based on results of ALU; 4 common bits: Zero, Negative, Overflow, Carry


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A microprocessorControl unit made up of:

Memory Address Register (MAR) holds current address where µp is accessing

Memory Data Register (MDR) holds instruction temporarily

Program Counter (PC) holds next instruction address to be read from the program memory (flash memory). Generally the counter increments each time an instruction is executed

Instruction Register (IR) The instruction at the address specified by the PC is read to this register. This operation is called a FETCH.

Control Logic (CL) synchronisation


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A microprocessor

Instruction fletch cycle


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Microcomputer systemµp + memory + i/o chips = µcomputer system

Memory devices – store program, dataI/O devices – read input and/or display results

Connected via buses. 3 types:Address (ex: 16-bit, unidirectional)Data (ex: 8-bit, bidirectional)Control (variable) e.g. Read, Write, Enable


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Microcomputer system

MPU

ROM(program)

RAM(data) PROGRAMMABLE I/O

Control lines

16-bit address bus

8-bit data bus


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Micro-controllerMicrocontrollers contain all of the functional sections (CPU, RAM, ROM, I/O, ports and timers) of a personal computer on a single integrated circuit. some people describe them as special purpose computers with several qualifying distinctions that separate them from other computers. Microcontrollers are "embedded" inside some other device (often a consumer product: kitchen appliances, TVs, VCRs, cameras, telephones) so that they can control the features or actions of the product.


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Micro-controller


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Building blocks of a microcontroller

Memory unitCentral Processing UnitBusInput-output unitSerial communicationTimer unitWatchdogAnalog to Digital Converter


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Building blocks: Input-output unit

When working with ports, first of all it is necessary to choose which port we need to work with, and then to send data to, or take it from the port

By selecting the appropriate register


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Building blocks: Serial communication


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Building blocks: Timer unit Timer unit can give information about time, duration, protocol etc.


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Building blocks: Watchdog This timer watches over the normal operation of the microcontroller software. It must be regularly cleared by software. When it times out the microcontroller returns to the point in the program immediately after power on. This timer is used to recover program operation when the software has a defect (or bug). Even if the program is reinitialized the bug is still in the program.


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Building blocks: Analog to Digital Converter

Analog to Digital Converter is responsible for converting an information about some analog value to a binary number and for follow it through to a CPU block so that CPU block can further process it.

Not available with all µP


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Embedded Systems: General Block Diagram

Microcontroller(uC)

sensor

sensor

sensor

Sensor conditioning

Output interfaces

actuator

indicator


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History in Brief1959: first IC's1971: µP 4004 4Bit Intel (~2000 Tr.)1972: µP 8008 8Bit Intel (~5000 Tr.)1974: µP 8080 8Bit Intel (~6000 Tr.)1974: µP 6800 8Bit Motorola1975: µP Z80 8Bit Zilog1976: µP 9900 16Bit Texas Instruments1978: µP 8086 16Bit Intel (50.000 Tr)1982: µP 8286 16Bit Intel (100.000 Tr.)1985: µP 80386 16Bit Intel (300.000 Tr.)1989: µP 80486 16Bit Intel (106 Tr.)1993: µP 80586 16Bit Intel (5·106 Tr.) ...


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Common MicrocontrollersFamiliesThere are several families of microprocessors are widely used in industrial control systems

Zilog Z8 seriesIntel 8051 seriesARM 32 bit microcontrollersMicroChip – PIC microcontrollers


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PICRange of low end 8 bit microcontrollers.smallest have only 8 pins, largest 40 pins.Typical chip is an 18 pin one.Very cheap, you can pick them up at less than Rs.500 each.Targeted at consumer products, burglar alarms etc.


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PIC MicrocontrollersThe term PIC stands for Programmable Interface Controller.PIC microcontrollers have become very popular because

Relatively cheapSmall in sizeOn chip memoryEasy to programReusable


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PIC Microcontroller Architecturevon Neumann architecture

programs and data share a single memory area that is accessed over a common bus

Harvard architecture separate memory areas and buses for data and programs

von Neumann Architecture. Harvard Architecture.

Note : PIC microcontroller follows Harvard design


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PIC Microcontroller Characteristics

CPUs8-bit16-bit

Number of I/O pins: 4-70Some chips have A/D converter and PWM

Memory types and sizes:Flash; OTP; ROM0.5k – 256k


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PIC Microcontrollers: Memory varieties Microchip produces field programmable microcontrollers in three basic varieties

EPROMcan be programmed electrically and erased, if needed, by a special ultraviolet light (window type)

OTPcan be programmed only once and is the least expensive of the three

Flash can be both programmed and erased by electrical means


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PIC Microcontrollers: Memory varietiesEx:

The PIC Family: SpeedPICs require a clock to work.

Can use crystals, clock oscillators, or even an RC circuit.Some PICs have a built in 4MHz RC clock

Not very accurate, but requires no external components

Instruction speed = 1/4 clock speed Tcyc = 4 * Tclk


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The Minimum PIC SystemYou need some kind of a clock:

Internal 4MHz clock on some PICs, external RC, external crystal, or external clock oscillator.

And you need some power:Most PICs can operate from 2.5V - 5.5V (see Data Sheets)New 16HVXX can directly use up to 14V(Great for direct 9V or 12V battery hook ups


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PIC Microcontrollers: Oscillator

If the CPU is the brain of the system then the oscillator, or clock, is the heartbeat. It provides the critical timing functions for the rest of the chip. The original version of the 16F84 can operate at up to 4-MHz while the newer chip has a 20-MHz upper limit. This section of the PIC is extremely versatile. There are three principal ways to clock a PIC chip.


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PIC Microcontrollers: Oscillator cont..There are three principal ways to clock a PIC chip.

Crystal controlled oscillator


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PIC Microcontrollers: Oscillator cont..

RC oscillator

Note: Not as precise as Xtal oscillator


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PIC Microcontrollers: Oscillator cont..External clock

Note: This is useful when the chip must be synchronized with other components or an entire system must be operated from a single clock source


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PIC Microcontrollers: PIC 16F84APIC16F84A belongs to a class of 8-bit microcontrollers of RISC architecture. Its general structure is shown below.

Microcontrollers with Harvard stands for. architecture are also called "RISC microcontrollers". RISC - Reduced Instruction Set Computer


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PIC Microcontrollers: PIC 16F84A


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PIC Microcontrollers: PIC 16F84

Program memory (FLASH) for storing a written program.

Since memory made in FLASH technology can be programmed and cleared more than once, it makes this microcontroller suitable for device development.

EEPROM - data memory that needs to be saved when there is no supply.RAM - data memory used by a program during its execution.

In RAM are stored all inter-results or temporary data during run-time.


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PIC Microcontrollers: PIC 16F84

PORTA and PORTB are physical connections between the microcontroller and the outside world. Port A has five, and port B has eight pins.FREE-RUN TIMER is an 8-bit register inside a microcontroller that works independently of the program. On every fourth clock of the oscillator it increments its value until it reaches the maximum (255), and then it starts counting over again from zero.CENTRAL PROCESSING UNIT The PIC has only 35 opcodes in its instruction set compared with more than 256 for a DEC Vax system6.


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PIC 16F84 : Pin description PIC16F84 has a total of 18 pins.


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PIC 16F84 : Pin description

Master clear, active lowMCLR

Oscillator crystal inputsOSC1,OSC2

Power supply ground reference (ss – source, dd drain)Vss , Vdd

8 bits of bidirectional I/O Port BRB[0-7]

5 bits of bidirectional I/O Port ARA[0-4]DescriptionPin Identifier


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PIC 16F84 A : FeaturesOnly 35 single word instructions to learn

All instructions single-cycle except for program branches which are two-cycle

Operating speed: 4 MHz clock input, 200 ns instruction cycle1024 words of program memory68 bytes of Data RAM64 bytes of Data EEPROM14-bit wide instruction words8-bit wide data bytes


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PIC 16F84A : Features15 Special Function Hardware registersEight-level deep hardware stackDirect, indirect and relative addressing modesFour interrupt sources:

External RB0/INT pinTMR0 timer overflowPORTB<7:4> interrupt-on-changeData EEPROM write complete


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PIC 16F84A : Peripheral Features13 I/O pins with individual direction controlHigh current sink/source for direct LED drive

25 mA sink max. per pin25 mA source max. per pinTMR0: 8-bit timer/counter with 8-bit

programmable prescaler


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PIC 16F84A: Program memory

The figure below shows the register file map inside the PIC16F84A


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PIC 16F84 : Registers cont…

Bank 1 is used to control the actual operation of the PIC

for example to tell the PIC which bits of Port A are input and which are output. Bank 0 is used to manipulate the data.

To change from Bank 0 to Bank 1 we tell the STAUS register.

We do this by setting bit 5 of the STATUS register to 1.To switch back to Bank 0, we set bit 5 of the STATUS register to 0.The STATUS register is located at address 03h (the ‘h’means the number is in Hexadecimal).


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PIC16F877A : Features

5/6 Programming pins8 A/D channels2 Oscillator Inputs2 RS-232 inputs33 I/O ports


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PIC Programming Language that microcontroller and man use to communicate is called "assembly language". Programs written in assembly language must be translated into a "language of zeros and ones" in order for a microcontroller to understand it (hex file). "Assembly language" and "assembler" are two different notions.

The first represents a set of rules used in writing a program for a microcontroller, the other is a program on the personal computer which translates assembly language into a language of zeros and ones.

A program that is translated into "zeros" and "ones" is also called "machine language". There are commercial software which could convert a C or Basic code in to PIC assembly language


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PIC programming : Assembler

The assembler expects to find specific terms in three columns.

First column: LabelsSecond column: opcodes and assembler directivesThird Columns & more: operands

The three columns are used in five ways.Header sectionEquates sectionOrigin sectionProgram sectionThe end statement.


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PIC programming : AssemblerLabels

A label is a mnemonic symbol assigned to an address.Ex : portb means port B whose real hexadecimal address is 0x06.Rules for defining labels

Must be positioned in the first columnMust begin with an alpha characterMay contain numeric, underscore or question markMay be up to 31 characters


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PIC programming : AssemblerLiterals

Literals are constants or numbers, usually hexadecimal numbers. Ex:

start movlw 0x00Literal

InstructionLabel


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Header

list radix

p=16f84 hex

Assembler directive


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PIC programming : AssemblerHeader

The information at the top of the source file is called a header.

;=========== pict1.asm===========list p=16f84radix hex

;-----------------------------------------------------------first line defines the type of PIC to be usedSecond line says that the number system is hexadecimal


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Equates

equ

Hex address or numberLabel This is an equates


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EquatesEquates are used to assign labels to addresses and names to numbers

Ex: portb equ 0x06

min equ 1 ; min =bit 1flag equ 0x0c ; flag = file register

Label

Hexadecimal address

Tells assembler this is an equate


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Origin

org

Hex address Not used This is an origin


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PIC programming : AssemblerOrigin

Usually origin statements used for three purposes.

Defines where the program code startsorg 0x000

To establish the reset vector

org 0x1ffgoto start

To establish the start of an interupt service

org 0x004


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Program

org

Literal or labelLabel Instruction


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EndThis is end

end


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PIC programming : AssemblerProgram formatStandard header

Equates

Program

Endend


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PIC programming : AssemblerAssembler files

All source code files must be saved with the file extension .asm.

ex: pic_1.asmAssembler creates two from the source code

.lst (assembler generated listing)

.hex (hexadecimal object code which can be downloaded to the chip)


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PIC programming : AssemblerThe assembler program reads each text file line , ignores it if begins with a semicolon and steps through the three columns.Style

list PIC16f84radix hex

portb equ 0x06org 0x06

Start movlw 0x00tris portbmovewf portb

circle goto circleend


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PIC Programming The process of communication between a man and a microcontroller

In order to do this we have to use a development system


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Development SystemsDevelopment SystemsMPLABMPLAB™™

EmulateMPLAB-ICE®PICMASTER®

ICEPIC

C CompilerAssembly

ProgramPRO MATE II ®PICSTART+®

SimulateMPLAB™SIM

Edit ProjectMPLAB™


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Development Systems

MPLAB-ICEPICMASTER®

ICEPICMPLAB-SIMPICSTART PlusPRO MATE® II


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Development SystemsUpgrades done in MPLAB software - firmware upgrades occasionally required for new PICmicrosub-familiesUses serial programming algorithms for all ICSP

capable devices

PICSTART PICSTART PlusPlusDEVELOPMENT PROGRAMMERDEVELOPMENT PROGRAMMER

POWERPOWERACTIVEACTIVE

RSRS--232 Serial 232 Serial InterfaceInterface 9V DC Input9V DC Input

Power ONPower ONProgrammerProgrammerActiveActive

4040--Pin ZIF Socket to accommodate Pin ZIF Socket to accommodate PICmicrosPICmicros from 8from 8-- to 40to 40--pins. 68pins. 68--pin PLCC pin PLCC can be programmed with an adaptercan be programmed with an adapter

PinPin--11


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PIC16F848-bit RISC (35 instructions, pipelined)Program counter 13-bit (points to the current instruction, automatically incremented)

Stack to support subroutines/interrupts can hold 8 levels of PC

MemoryProgram memory (FLASH) 1024, 14-bit locationsData Memory

RAM: 68, 8-bit locationsEEPROM: 64, 8-bit locations (slow write access)


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PIC programming : PIC16F84 instruction setPIC16F84 has 35 instruction in its instruction set

Move or define data

Note : k is a constant, f is the file register, d is destination-0 for w register and 1 for file register fNothing


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Changing register content


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Control program flow


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Control Microcontroller


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Logic


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PIC programming : PIC16F84 instruction setPIC16F84 has 35 instructions in its instruction set

Arithmetic

Software: Programmers Model

Program Memory

“Burned” in by programmer (can’t

change during execution). Stored

instructions, addresses and “literals” (numbers).

<- 12/14/16 bits ->

Hardware StackStores addresses for subroutines

Program Counter-PCL(PCH)

Status

Special PurposeRegisters

I/O pin states, peripheral registers, etc.

General PurposeRegisters

RAM or “data memory”. Variables are

stored here.

W “Register”

<- 8 bits ->


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Microcontroller Architecture


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PIC16F84 : An Example Code

Port configurationTRISA or TRISB are used to configure Port A and Port B respectivelyIf a bit of TRSA is is high, corresponding pin of the Port A is configured as input, otherwise it is an outputEx: To configure pins 0 and 3 of Port A as outputs and 1 and 2 inputs

BSF 03h,5 ;Go to Bank 1MOVLW 06h ;Put 00110 (06h) into WMOVWF 85h ;Move 00110 onto TRISABCF 03h,5 ;Come back to Bank 0

Note : see the memory map for the address, only the program section is shown


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Software: Instruction Examples

movlw 0xFF

Move (“mov”) the number (“l” for “literal”) 0xFF - that’s 256 in decimal- into the working register (“w”).

In other words, load W with the value 0xFF.


Program Memory

<- 12/14/16 ->

Hardware Stack


Status



W “Register”

<- 8 bits ->

0xFF


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PORTA 05hmovwf PORTA

Move (“mov”) the working register (“w”) into the file register(“f”) named PORTA.

In other words, load the register called PORTA with whatevernumber is in the W register.


Program Memory

<- 12/14/16 ->

Hardware Stack


Status


PORTA


W “Register”

<- 8 bits ->

Value in W


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movfPORTA, W

Move (“mov”) the the value of the file register (“f”) named PORTA into the working register (“w”) .

In other words, load W with the whatever number is in PORTA.


Program Memory

<- 12/14/16 ->

Hardware Stack


Status


PORTA


W “Register”

<- 8 bits ->

Value in PORTA


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Writing values to port A

bcf 03h,5 ;Come back to Bank 0Start movlw 02h ; Write 02h to the W register. In binary this is

; 00010, which puts a ‘1’ on pin 2 while; keeping; the other pins to ‘0’

movwf 05h ;Now move the contents of W (02h) oto the;PortA, whose address is 05h

movlw 00h ;Write 00h to the W register. This puts a ‘0’ on;all pins.

movwf 05h ;Now move the contents of W (0h) onto the;Port A whose address is 05h

goto Start ;Go to where we say Startend


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PIC16F84 : An Example Code STATUS equ 03h ;this assigns the word STATUS to the value of 03h,

;which is the address of the STATUS register.TRISA equ 85h ;This assigns the word TRISA to the value of 85h,

; which is the address of the Tri-State register for PortAPORTA equ 05h ;This assigns the word PORTA to 05h which is the

;address of Port Absf 03h,5 ;Go to Bank 1movlw 00h ;Put 00000 into Wmovwf 85h ;Move 00000 onto TRISA – all pins set to outputbcf 03h,5 ;Come back to Bank 0

Start movlw 02h ;Write 02h to the W register. In binary this is;00010, which puts a ‘1’ on pin 2 while keeping

;the other pins to ‘0’movwf PORTA ;Now move the contents of W (02h) onto the

;PortA, whose address is 05hmovlw 00h ;Write 00h to the W register. This puts a ‘0’ on

;all pins.

movwf PORTA ;Now move the contents of W (0h) onto the Port A

; whose address is 05hgoto Start ;Go to where we say Startend


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PIC16F84 : Hardware implementation

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