book - BACA13 - Introduction to Microcontroller Programming in C

8/7/2019 book - BACA13 - Introduction to Microcontroller Programming in C

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Student name:_______________________

Hands-On Technical Training (HOTT) Workshop:Introduction to Microcontroller Programming in C

Rev. 10JULY2008

Table of Contents

Hands-On Technical Training (HOTT) Workshop:Introduction to Microcontroller Programming in C .............................................................1

Table of Contents .............................................................................................................1How to Use this Training Material if provided on CD or in Zipped File: .......................3Workshop objectives: .......................................................................................................3What is an Embedded Controller? ................................................................................... 4

What is a Microcontroller? .............................................................................................. 4Microcontroller Advantages ............................................................................................ 4

Microcontroller Disadvantages ........................................................................................ 4Microcontroller Architecture Example ............................................................................5Microcontroller Selection Considerations ....................................................................... 5Lab Setup for this Workshop ........................................................................................... 7Programming Language Considerations ..........................................................................7A Brief Introduction to the C Programming Language ................................................... 8

Data Types ................................................................................................................... 8Declaring Variables and Assigning an Initial Value ....................................................8

Comparison ................................................................................................................10Logical Connectors .................................................................................................... 11The if else Statement ..................................................................................................11Loops ..........................................................................................................................12The for Loop .............................................................................................................. 13Functions in C ............................................................................................................13

Freescale IDE Software Installation .............................................................................. 16Hardware Familiarization and Connection to PC ..........................................................16Understanding the RS08 I/O .......................................................................................... 17Launching & Exploring the IDE ....................................................................................19

Creating a new project ...............................................................................................19Configuring the Microcontroller Chip for Proper Operation with the DevelopmentBoard ..........................................................................................................................23Editing and Downloading a Program .........................................................................25Modifying the Program to Slow Down the LED1 Blink Rate ...................................28

Debug Tools: Monitoring, I/O, Breakpoints, and Other Neat Stuff .............................. 30Monitoring the Program & I/O .................................................................................. 30Using Breakpoints ......................................................................................................31


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Stand-alone uC Circuit Example:Minimum Circuit Required for the Hello World Example Program .........................32

Links to Executable Programming Examples Provided with this Training Material (CDor unzipped directory) ....................................................................................................33Additional Resources .....................................................................................................35

Documents Provided with this Training Material (CD or unzipped directory) .........35Online Resources .......................................................................................................35Support ....................................................................................................................... 35Purchasing Your Own Demo Kits and Microcontrollers ...........................................35

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How to Use this Training Material if provided on CD or in ZippedFile:

1. Unzip if necessary and copy entire root directory of all files to your PC harddrive.

2. Open this document file in your web browser. There are hyperlinks locatedthroughout that will enrich your user experience.

Workshop objectives:

1. Learn what a microcontroller is and some typical applications.2. Learn some criteria to consider when selecting a microcontroller.3. Learn fundamental microcontroller programming in the C language.4. Learn how to use a typical C Compiler and IDE (Integrated Development

Environment) for developing microcontroller applications.

5. Learn the basics of C programming by editing various C programs and testingthem on an actual Freescale RS08 microcontroller.

Prerequisites: None, but some programming experience is helpful, especially C, C++, or C#.

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What is an Embedded Controller?

As stated at http://www.esacademy.com/automation/faq/primer/2.htm:

An embedded controller is basically a controller (typically a microcontroller,microprocessor, or computer) that is embedded into some [system or] device forsome purpose other than to provide general purpose computing.

This device would be called an Embedded Control System. Some examples might be ahome appliance or toy with a microcontroller inside of it or a factory automation systemthat contains a dedicated computer control box.

What is a Microcontroller?

According to wikipedia:

A microcontroller (also MCU or C) is a computer-on-a-chip. It is a type ofmicroprocessor emphasizing self-sufficiency and cost-effectiveness, in contrast to

a general-purpose microprocessor (the kind used in a PC). In addition to all

arithmetic and logic elements of a general purpose microprocessor, the

microcontroller usually also integrates additional elements such as read-only andread-write memory, and input/output interfaces.

Microcontroller Advantages

Highly integrated and powerful thousands of transistors on a single chip.

Can be used to replace a handful of discrete logic chips.

Relatively easy to learn and implement.

Easier to integrate into a design than discrete logic chips.

Very low hardware cost possible (the RS08KA2 microcontroller chip used in thislab costs less than $0.50 each in large quantities!).

Many types and manufacturers available.

Architectures and programming languages vary somewhat, but not completely, sowhat you learn about one microcontroller (uC) is good knowledge to apply toanother one.

Many different IC packages available (DIP8, SOIC-16, etc.)

Microcontroller Disadvantages

Microcontrollers are IC chips and need to be put onto a custom-designed PCboard. This takes time and money, which may not suit all applications. Contrastthis with an industrial automation PLC, which is a computer-in-a-box thatcontains simple screw terminals to connect power, communication, and I/O.

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Programming microcontrollers requires a certain amount of skill and training.

The programming and debugging software can be quite costly.

Microcontroller Architecture ExampleAn example of a simple microcontroller is shown here embedded in a system:

Microcontroller Selection Considerations

The following list shows items to be considered when selecting a microcontroller. Eachapplication will be unique, so some of these considerations may not apply.

I/O count and typeo Digital?

o Analog

Number of inputs and outputs?

Resolution?

Conversion time?

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Memory

Areas

Input/Output (I/O) Section

CoreMicroprocessor

Timers

&Counters

Freescale RS08KA2 Microcontroller Chip

To other electronic devices (pushbuttons,LEDs, speakers, etc.)

Embedded Control System

InterruptControl

Subs stem

AnalogComparator


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Voltage range?o PWM?

o Interrupts?

o Output drive current?

o Logic voltage levels?

Amount of on-chip memory? External memory

o Possible?

o Maximum amount?

Supply voltage range and current required?

Bus speed?

Floating point (real number) math support?

Timers quantity, resolution, maximum time?

Other special functions needed?

Rated temperature range?

Cost per device? Manufacturers sampling policy?

Development toolso Cost?

o Features?

o Many types of chips supported or just one or two?

o Additional adapters needed (at what cost?) to use with other chips in same

family?o Can it be easily connected to in-circuit chips?

Programming softwareo Cost?

o IDE (Integrated Development Environment) learning curve?

o Programming language(s) supported C, Assembly, Java, BASIC, etc.?

o Support email, online, phone, etc.?

o Does it support different chips by same manufacturer, or might different

versions be needed later for higher end chips?o Does it have a built-in chip simulator?

Prior experience with chip, manufacturer, or software?

Application notes and reference designs online?

Reputation of manufacturer?

Support

o Email?o Online?

o Phone?

o Forums?

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Lab Setup for this Workshop

For this workshop, we will be using the following hardware and software:1. The low-end Freescale RS08 microcontroller,2. An inexpensive but effective development board called the DEMO9RS08KA2,

3. and the CodeWarrior IDE/C Compiler.

The RS08 chip is simple but effective for learning the basics of microcontrollers. It isalso well documented and suits a variety of end-user applications.

Programming Language Considerations

The C language is currently the most popular programming language for embeddedcontrol using microcontrollers. This language offers a good balance of being relativelyeasy to learn yet able to perform powerful low-level functions such as bit-level I/O.

Freescale offers the CodeWarrior C compiler free of charge for use with the RS08 and anumber of other Freescale microcontrollers and microprocessors. Very few othermanufacturers offer a free C compiler, with many costing several hundred dollars or moreper license. Note that Freescale charges a fee for the C compiler required for higher endmicrocontrollers. Zilog is another microcontroller manufacturer that offers a free Ccompiler, so they may be worth considering for cost conscious applications. Oneadvantage of the Freescale CodeWarrior IDE compared to Zilogs IDE is that Freescaleincludes a very nice hardware configuration GUI. Youll see that up close in just a littlewhile.

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A Brief Introduction to the C Programming Language

(some of this information was borrowed from http://www.imada.sdu.dk)Copyright Notice and Credits The University of Strathclyde, Glasgow, Scotland.Permission to copy is granted provided that these credits remain intact.These notes were written by Steve Holmes of the University of Strathclyde Computer Centre. They originally formed the basis of the Computer Centre's

C programming course. Steve no longer works for the University of Strathclyde, and we are unable to answer queries relating to this course. You arewelcome to make links to it however, but please bear in mind that it was written for students within the University and so some parts may not be relevantto external readers.

C is case sensitive.

C allows programmers to separate the code into functions, which are similar tosubroutines but more powerful. More info about that in a little while.

Data Types

Below is a partial list of numeric data types supported by the C language.

Data Type Abbreviation Range

Integer int -32,768 to 32,767

Short short -32,768 to 32,767

Long long -2,147,483,648 to 2,147,483,647

Unsigned int uint 0 to 65,535

Byte byte 0 to 65,535

Unsigned long ulong 0 to 4,294,967,295

Floating point float 10-37 to 1037

Declaring Variables and Assigning an Initial Value

Before a variable may be used in a C program, it must be declared by name (i.e., created)and given a data type. Here is an example of a variable declaration:

int LoopCount;

In this declaration, the data type is int for integer.The variable name is LoopCount. This variable may be used in the program from thispoint forward.Finally, note that the instruction must end with a semicolon. This is generally true ofC instructions.

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While the declaration is not required to assign a value to the variable, it is a very goodidea to do both together. Therefore, this is a better declaration, which also contains anassignment statement:

int LoopCount = 0;

The variable LoopCount is declared and assigned a value of zero.

Arithmetic OperatorsHere are the most common arithmetic operators

*, / and % will be performed before + or - in any expression. Brackets can be used to

force a different order of evaluation to this. Where division is performed between twointegers, the result will be an integer, with remainder discarded. Modulo reduction is onlymeaningful between integers. If a program is ever required to divide a number by zero,this will cause an error, usually causing the program to crash.

Here are some arithmetic expressions used within assignment statements:

velocity = distance / time;

force = mass * acceleration;

count = count + 1;

C has some operators which allow abbreviation of certain types of arithmetic assignmentstatements.

These operations are usually very efficient. They can be combined with anotherexpression.

Versions where the operator occurs before the variable name change the value of thevariable before evaluating the expression, so

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These can cause confusion if you try to do too many things on one command line. Youare recommended to restrict your use of++ and - to ensure that your programs stay

readable.

Another shorthand notation is listed below

Comparison

C has no special type to represent logical or boolean values. It improvises by using any ofthe integral types char, int, short, long, unsigned, with a value of 0 representing false andany other value representing true. It is rare for logical values to be stored in variables.They are usually generated as required by comparing two numeric values. This is wherethe comparison operators are used, they compare two numeric values and produce alogical result.

Note that == is used in comparisons and = is used in assignments. Comparison operatorsare used in expressions like the ones below.

x == y

i > 10

a + b != c

In the last example, all arithmetic is done before any comparison is made.

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These comparisons are most frequently used to control an if statement or a for or a whileloop.

Logical Connectors

These are the usual And, Or and Not operators.

They are frequently used to combine relational operators, for example

x < 20 && x >= 10

In C these logical connectives employ a technique known as lazy evaluation. Theyevaluate their left hand operand, and then only evaluate the right hand one if this isrequired. Clearly false && anything is always false, true || anything is always true. Insuch cases the second test is not evaluated.

Not operates on a single logical value, its effect is to reverse its state. Here is an exampleof its use.

ReadyLight = !HeaterActive;

The if else Statement

This is used to decide whether to do something at a special point, or to decide betweentwo courses of action.

The following test decides whether a student has passed an exam with a pass mark of 45

if (result >= 45)printf("Pass\n");

elseprintf("Fail\n");

It is possible to use the if part without the else.

if (temperature < 0)print("Frozen\n");

Each version consists of a test, (this is the bracketed statement following the if). If the testis true then the next statement is obeyed. If it is false then the statement following the elseis obeyed if present. After this, the rest of the program continues as normal.

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If we wish to have more than one statement following the if or the else, they should begrouped together between curly brackets. Such a grouping is called a compoundstatement or a block.

if (result >= 45){ printf("Passed\n");

printf("Congratulations\n")}else{ printf("Failed\n");

printf("Good luck in the future!\n");}

Sometimes we wish to make a multi-way decision based on several conditions. The mostgeneral way of doing this is by using the else if variant on the if statement. This works bycascading several comparisons. As soon as one of these gives a true result, the following

statement or block is executed, and no further comparisons are performed. In thefollowing example we are awarding grades depending on the exam result.

if (result >= 75)printf("Passed: Grade A\n");

else if (result >= 60)printf("Passed: Grade B\n");

else if (result >= 45)printf("Passed: Grade C\n");

elseprintf("Failed\n");

In this example, all comparisons test a single variable called result. In other cases, eachtest may involve a different variable or some combination of tests. The same pattern canbe used with more or fewer else if's, and the final lone else may be left out. It is up to theprogrammer to devise the correct structure for each programming problem.

Loops

C gives you a choice of three types of loop, while, do while and for.

The while loop keeps repeating an action until an associated test returns false.

This is useful where the programmer does not know in advance how many timesthe loop will be traversed.

The do while loops is similar, but the test occurs after the loop body is executed.This ensures that the loop body is run at least once.

The for loop is frequently used, usually where the loop will be traversed a fixednumber of times. It is very flexible, and novice programmers should take care notto abuse the power it offers.

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The for Loop

The for loop works well where the number of iterations of the loop is known before the

loop is entered. The head of the loop consists of three parts separated by semicolons.

The first is run before the loop is entered. This is usually the initialization of theloop variable.

The second is a test, the loop is exited when this returns false. The third is a statement to be run every time the loop body is completed. This is

usually an increment of the loop counter.

The example is a function which calculates the average of the numbers stored in an array.The function takes the array and the number of elements as arguments.

int count;

for (count = 1; count


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Here is a function which raises a double to the power of an unsigned, and returns theresult.

double power(double val, unsigned pow){ double ret_val = 1.0;

unsigned i;

for(i = 0; i < pow; i++)ret_val *= val;

return(ret_val);}

The function follows a simple algorithm, multiplying the value by itself pow times. A forloop is used to control the number of multiplications, and variable ret_val stores the valueto be returned. Careful programming has ensured that the boundary condition is correcttoo.

Let us examine the details of this function.

double power(double val, unsigned pow)This line begins the function definition. It tells us the type of the return value, the nameof the function, and a list of arguments used by the function. The arguments and theirtypes are enclosed in brackets, each pair separated by commas.

The body of the function is bounded by a set of curly brackets. Any variables declaredhere will be treated as local unless specifically declared as static or extern types.

return(ret_val);

On reaching a return statement, control of the program returns to the calling function. Thebracketed value is the value which is returned from the function. If the final closing curlybracket is reached before any return value, then the function will return automatically,any return value will then be meaningless.

The example function can be called by a line in another function which looks like this

result = power(val, pow);

This calls the function power assigning the return value to variable result.

Here is an example of a function which does not return a value.

void error_line(int line){ fprintf(stderr, "Error in input data: line %d\n", line);}

The definition uses type void which is optional. It shows that no return value is used.Otherwise the function is much the same as the previous example, except that there is noreturn statement. Some void type functions might use return, but only to force an early

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exit from the function, and not to return any value. This is rather like using break to jumpout of a loop.

This function also demonstrates a new feature.

fprintf(stderr, "Error in input data: line %d\n", line);This is a variant on the printf statement, fprintf sends its output into a file. In this case,the file is stderr. stderr is a special UNIX file which serves as the channel for errormessages. It is usually connected to the console of the computer system, so this is a goodway to display error messages from your programs. Messages sent to stderr will appearon screen even if the normal output of the program has been redirected to a file or aprinter.

The function would be called as follows

error_line(line_number);

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Freescale IDE Software Installation

The necessary software, Special Edition: CodeWarrior for Microcontrollers, is alreadyinstalled on the computers in this lab, so we wont be installing it today. However, if youwant to download and install the free IDE/Assembler/C compiler on your own PC, you

should go towww.freescale.com and search for keywords codewarrior formicrocontrollers special edition download, then look for the Download link. Theinstallation process is quite easy, though it may take the better part of an hour.

Note: If you purchased a demonstration board, that package may include a CD or DVDwith an earlier version of the IDE that does notinclude the C compiler. This should notbe installed.

If you purchase a development board like the one used in this lab, you will also need toinstall the USB drivers to enable the PC to communicate with the board.

Hardware Familiarization and Connection to PC

Demo board hardware is described in the demonstration board users manualon variouspages. Click the link and/or go to the manual, read the pages listed below, and answerthese questions:

1. Referring to the users manual section 1.3, what devices are supported by theDEMO9RS08KA2 development board?____________________________________________________

2. From PDF pages 9 & 10 (manual pages 7-8), briefly review the location of the

various items on the demo board, comparing your actual board to the drawing anddescription. Note that the programming target microcontroller is a socketed DIPthat may be removed after it is programmed. This is convenient for stand-aloneapplications. Also, realize that the majority of the board exists simply to supportcommunication with the PC and demo I/O (LEDs, pushbuttons, and NTCresistor). As a side note, Zilog handles this in a different way that some designersprefer.

3. Section 8 in the manual outlines the various jumper and connector settings.Review it briefly at this time and locate the connectors on your demo board. Ifyou are not familiar with this type of jumper, ask your lab instructor todemonstrate how it works.

4. Read through section 4.1, entitled First Connection, and go through the steps toverify the demo board jumper settings and connect the board to the PC USB port.

Emphasizing again, the microcontroller is one small chip on the development board. Therest of the board is fairly complex and exists to support USB communication with thehost PC. Without getting too concerned with the abbreviations right now, consider thisexample of a simple, stand-alone microcontroller application:

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Understanding the RS08 I/O

Look at Figure 2-2 in the RS08 data sheet. Most of the pins are multi-purpose, describedby terms such as PTA3/ACMPO/BKGD/MS. Refer to Table 2-1 and fill in the blanksbelow with the functions associated with each of these terms:

PTA3 (Port A, bit 3): ___________________________________ACMPO: __________________________________

BKGD: ___________________________________MS: ______________________________________

The data sheet table describes each of the RS08 pins and not just the PTA3 pin. Refer tothis as necessary throughout the lab if you are having problems understanding the pinnames and functions.

While youre on that page, right above Table 2-1 is a paragraph that says:

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Freescale RS08KA2microcontroller in

SMT package is the

embedded controllerin this music box
http://opt/scribd/conversion/tmp/scratch6661/MC9RS08KA2%20&%20KA1%20Data%20Sheet.pdfhttp://opt/scribd/conversion/tmp/scratch6661/MC9RS08KA2%20&%20KA1%20Data%20Sheet.pdf


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NOTE To avoid extra current drain from floating input pins, the resetinitialization routine in the application program should either enable on-chippullup/pulldown devices or change the direction of unused pins to outputs.

Two important points should be made here. First, typical of CMOS integrated circuitswith their high input impedance MOSFETs, the RS08 will possibly oscillate and/or drawexcess current if an input is left floating. Normally this is solved by tying any unusedinputs high or low. However, and this is the second point, the RS08 contains internalpullup and pulldown resistors (approx. 50-60 kilohms each) that may either be connectedor disconnected, depending upon the configuration (initialization) settings, which will beexamined in more detail shortly. Any pins configured as inputs should have theirinternal pullup or pulldown resistors connected unless the external circuitry makes

provision for pullup/pulldown. Remember that when you make configuration

settings in the software.

Section 2.4 in the data sheet provides a detailed explanation of each of the pins on thechip. Glance through it now.

Statements such as the following may be ignored unless you plan to handle deviceinitialization yourself through program code: To use as an output-only port, BKGDPE inSOPT must be cleared. This refers to initializing the device, or telling it which pins areinputs, outputs, etc., which is not normally a concern since device initialization is handledthrough a very nice GUI (Graphical User Interface) in the IDE. That tool enables RS08programmers to easily generate device initialization code, which runs once when themicrocontroller begins program execution.

Refer to the schematic for the demo board, which is in a separate document, and drawlines in the following table connecting each microcontroller pin listed in the left columnto its corresponding development board component on the right. The first one has beendone for you.

PTA0/KBIP0/ACMP+ SW0PTA1/KBIP1/ACMP RESETPTA2/KBIP2/TCLK/RESET/VPP NTCPTA3/BKGD/MS/ACMPO LED1PTA4/KBIP4 LED2PTA5/KBIP5 LED0

The bold items in the list above are the settings required for connection to the deviceslisted on the right. These settings would be made using the Device Initialization tool.

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Launching & Exploring the IDE

Creating a new project

1. Launch CodeWarrior IDE from desktop icon. This is the PC application forprogramming and debugging the microcontroller.

2. If the Startup window dialog box appears, select Create New Project. If not,select File > Startup Dialog, then click Create New Project.

3. Refer to the diagram below. In the New Project dialog box, expand the left-sidetree and select the MC9RS08KA2 device. This is the microcontroller youll beprogramming.

4. Select the SofTec RS08 for the default connection and click Next.5. Select C as the programming language and no others.6. For the project name, type in Hello World.mcp as shown below, then set the

location to My Documents and click Next.

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7. The next step of the wizard asks you if you want to add existing files to yourproject. We dont need any pre-existing files for this project, so click Next again.

8. Recall that most of the pins on this microcontroller can serve multiple purposes.The Device Initialization tool (the GUI mentioned earlier) enables you to editthose pin assignments from within your project. Select Device Initialization asshown below and click Next.

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9. On the following screen, make sure the selections are set as illustrated below.This will cause the wizard to generate the necessary program files with code stubsto make your programming job easier. Also, floating point or real numbers willnot be used in this project, so that option should be deselected. Floats require alarge amount of memory and do not work well on the RS08 because of its verysmall memory area.

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10. Click Finish and the wizard will build your project.

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Configuring the Microcontroller Chip for Proper Operation with theDevelopment Board

1. The right side of the CodeWarrior IDE should display the Device Initializationtool illustrated below. If not, select from the menu Device Initialization >

Initialize Device.

2. We will now make some basic CPU settings. Click the CPU block in the DeviceInitialization GUI, which should open a new window where you will make those

changes.3. In the window that opens, expand the Internal Peripherals area and verify that

BDM pin support is Enabled. This allows debugging the microcontrolleroperation from the PC, which is a very nice programming feature that well beusing. If you look at the development board schematic, youll see that the debugpin is shared with one of the LEDs, so it will blink when the PC is communicatingwith the microcontroller. Incidentally, BKGD and BDM are interchangeable

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terms that both refer to the background debug pin. If the BDM pin support isDisabled, click the button on that row to enable it.

4. If the Reset pin support is Disabled, click the button on that row to enable it. Thiswill assign the Reset pin on the development board to recognize the Reset button.

5. Click OK to accept those CPU changes.

6. The CPU contains a special section called a Watchdog or Computer OperatingProperly (COP) that supervises operation of the CPU. Its a handy feature, but wewill not be using it at this time and so it must be disabled. Select the DeviceInitialization block labeled COP and change the Initialization option to EnableCOP no. Click OK.

7. PTA, or Port A, is Freescales name for the group of 6 I/O pins. Click the PTAblock to select this port and configure the pins.

8. Under Settings, Port Control, click the button on that row to change the settingfrom Entire I/O port to Individual pins. We will be configuring some pins asinputs and some pins as outputs.

9. Referring to the information you studied above and/or the demo board schematic,

note that SW0 is connected to microcontroller pin PTA1/KBIP1/ACMP. This pincan serve three purposes, as alluded to earlier. Since this pin is connected toswitch SW0, set it as Enabled with Direction set to Input. Looking ahead, thename PTAD_PTAD1 will be used in the program to refer to this input.

10. Again referring to the previous information, set the appropriate pins as Outputsfor LED1 and LED2. Your settings should appear as below.

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11. Click OK to accept the Port A changes. Notice that the Device Initializationblocks that have been changed from their default settings now appear aqua incolor.

12. Find and click the Generate Code button. This step is veryimportant because it commands the IDE to convert the changes you just made into

programming code that will be sent to the microcontroller. Read the additionaldialog boxes that pop up, accept the defaults for now, and use common sense torespond.

Editing and Downloading a Program

1. The left side of the IDE shows the overview of your new project. The mainprogram file is appropriately named main.c. Double click main.c to open it forediting. In this example, youll be writing a program to turn LED1 on and offwhen switch SW0 is pressed.

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Your main.c program file should appear something like this:

2. In the main.c file, there are several lines you should basically understand butdont need to change. First, there are some #include statements at the top of thefile. These were inserted automatically when the project was created and directthe compiler to compile those other files before compiling the main file. Theselines are necessary and should not be modified. Next, the line that begins withvoid MCU_init(void); is called a function prototype and tells the compiler the

signature of function MCU_init, which will be invoked soon. This is necessarybecause the function has not been compiled yet at this point. Remember thatevery line of program code in C must end with a semicolon. The compiler willnot be able to compile the files successfully if you dont follow this rule.

3. Next in the program is the line void main (void) { . This is the beginning of themain program routine, or function. The main function ends with a closing curlybrace, }.

4. The first line within this main function tells the processor to run the hardwareinitialization routine, MCU_init.c. If youre curious, double click that file name

in the project tree on the left under the folder Generated Code. All of theMCU_init.c code was generated by the Device Initialization tool and would haveto be generated by hand if that tool did not exist!

5. In main.c, find the line that contains the text/* include your code here */. This iscalled a comment, which is purely for human benefit and will be ignored by thecompiler. There are two types of comments used in C as shown in these twoexamples:

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// This is a comment. Double slashes tell the compiler to ignore// any text following the slashes on that one line only.

/* This slash-and-asterisk type of comment may cross over multiple lines

because the compiler treats everything within the opening and closing slash-

and-asterisk comment symbols as comments rather than executable code*/

6. Delete that /* include your code here */ comment, then locate the line for(;;){. This instruction defines the beginning of an infinite loop. Immediatelyfollowing thatline, insert the following lines of text, which are actual programcode:

if(!PTAD_PTAD1) // switch SW0 pressed?PTAD_PTAD4 = !PTAD_PTAD4; // yes. Reverse the state of LED1

The whole purpose of this little program, as the comments show, is to reverse thestate of LED1 each time SW0 is detected as being pressed on, off, on, off, etc.The exclamation point basically says take the inverse or opposite.

Recall that switch SW0 is connected to input PTAD_PTAD1 and LED1 isconnected to PTAD_PTAD4. The first line reads if(!PTAD_PTAD1). This meansif Port A Data Bit 1 is not on and determines whether the next line of code willexecute or not. If the parenthetical condition is true (i.e., if the pushbutton ispressed), then PTAD_PTAD4 = !PTAD_PTAD4; will run. If the SW0 button is notpressed, the if condition is false and the PTAD_PTAD4 line will be skippedover.

You may wonder why pressing the button makes the inverse of the input becometrue (input PTAD_PTAD1 = zero or logical FALSE if the button is pressed). If

you look at the schematic, youll see that the switch is tied to ground and so itpulls the input low when it is pressed. Also, pullup resistor R103 pulls the inputhigh when the button is not pressed. Therefore, !PTAD_PTAD1 is true when thebutton is pressed.

Now lets take a closer look at the PTAD_PTAD4 = !PTAD_PTAD4; statement. Thissays make output PTAD_PTAD4 equal to its inverse, which reverses the stateof the output bit. So, pressing the button reverses the LED state.

7. Select from the menu Project > Make (or F7 or this little icon: ). This will

compile the project files. No error messages should appear at this time.Optional: To create an error condition and see how the compiler responds, removeone of the semicolons in main.c and recompile the project.

8. Select Project > Debug (or F5 or green right arrow icon). Note: Selecting Debugwill automatically compile the project, so step #7 above was not really necessary,but was included for training purposes.

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9. In the MCU Configuration dialog window that pops up, select Hardware ModelDEMO9RS08KA2 and click OK. This will send your Hello World program tothe microcontroller on the demo board. The term for this is downloading.

10. The True-Time Simulator and Real-Time Debugger tool should now open in anew window. This tool is basically a panel from which to control and monitor

operation of the microcontroller. Once the program download is complete, lookat the toolbar and find the Run button, which is a green right arrow icon. Clickthis icon or press the F5 button to start the program execution.

11. Notice that the green Run button icon has become grayed out, indicating that theprogram is running. If it has not grayed-out, again click it or press F5.

12. The program should now be running. To test it, press and release the SW0pushbutton repeatedly while watching LED1. Note that LED1 seems to dimwhile SW0 is pressed, then when SW0 is released, LED1 may be either off or onrandomly. LED1 is actually blinking on and off while SW0 is held, but muchmore quickly than the human eye can detect. The program isnt quite right yet, soin the following steps youll modify it.

Modifying the Program to Slow Down the LED1 Blink Rate

1. Close the debugger tool and edit the main.c file in the CodeWarrior IDE.2. Modify your existing program (use copy & paste from this document if you

prefer) to look like this, with changes shown in bold text and pointed out with leftangle brackets:

#include /* for EnableInterrupts macro */#include "derivative.h" /* include peripheral declarations */

void MCU_init(void); /* Device initialization function declaration */

void main(void) {

int LoopCount = 0; // Declare and zero new integer variableMCU_init(); /* call Device Initialization */

for(;;) {for(LoopCount=0;LoopCount < 10000; LoopCount++); // delay here

if(!PTAD_PTAD1) // switch SW0 pressed?PTAD_PTAD4 = ~PTAD_PTAD4; // yes. Reverse the state of LED1

} /* loop forever *//* please make sure that you never leave main */

}

3. Download and retest your modified program. Note that it may not yet be perfect,but it works much better now and that LED1 on the development board changesstate each time SW0 is pressed. Also notice that LED1 blinks if SW0 is helddown continuously. Why?

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This program is not quite perfect yet, but it still works well enough for this example.The LED1 state change is not 100% predictable, but more code could be added to makeit work better. Lets just keep it simple at this point and enjoy the example for what it is.

4. Modify and test your program again by replacing the LoopCount < 10000 witheach of the following to see which value works best:a. LoopCount < 32767b. LoopCount < 1000c. LoopCount < 100

These program additions work as follows. First, the new integer variable LoopCount isdeclared(i.e., created) and initialized or assigned a value zero here:

int LoopCount = 0;

Several important notes about declaring variables:1. The syntax is very important and must include the data type (int forinteger in this example), variable name (e.g., LoopCount), and the endingsemicolon. The initialization ( = 0 ) sets the variable equal to some value (zeroin this case). Declarations do not need to include initialization, but manyprogrammers prefer to always initialize variables at the same time they aredeclared because this will avoid certain programming problems later.2. Any variable declarations must precede any executable code in a function.Notice that the LoopCount declaration precedes the call to the MCU_init functionwithin the main function. The order of these lines may not be reversed or thecompile will fail. Try it right now if youd like.3. It is necessary to declare a variable before it is used in a program. Thisnew LoopCount variable is used in the main routine and therefore it needed to bedeclared first.

The new line for(LoopCount=0;LoopCount < 10000; LoopCount++); // delay here wasadded to slow down the program. The for instruction works this way:

1. LoopCount=0 sets that variable to an initial value of zero,2. LoopCount < 10000 checks the value of the variable. If it is less than the target

value (10000), then the next instruction(s) following the for instruction will beexecuted. In this case, the for instruction is followed by a semicolon rather thansome instruction to be looped, so this loop does nothing but waste time. WhenLoopCount reaches 10000, the processor exits the loop and continues program

execution at the next line following the for loop.3. LoopCount++ simply increments the LoopCount value by one after each loop is

executed.4. The net result is that LoopCount starts at zero, counts up to 10000, then the loop

instruction is finished and the program continues.

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Debug Tools: Monitoring, I/O, Breakpoints, and Other Neat Stuff

Monitoring the Program & I/O

1. Press F5 to download and debug the latest version of your Hello World testprogram.

2. In the Debugger window, notice the upper left panel is labeled Source andcurrently contains the main.c program source code.

3. The panel below that panel is labeled Procedure and is sometimes referred to asthe Call Stack. This panel displays the function currently being executed at thetop of the list and then the path it took to get there. Hold that thought and thendirect your attention back to the panel containing main.c. Press the F11 button(single step) once. The highlighting in main.c should have moved forward in theinstruction list, indicating that the next instruction to be executed is MCU_init();, which is a call to function MCU_init. A call is the same as a JUMPSUBROUTINE or GOSUB in other programming languages. Think of MCU_initas a subroutine that runs only once when the uC first begins program execution.

4. Press F11 again and notice how the Source and Procedure panels both change.The uC is now executing the MCU_init function.

5. Press F11 a few more times, noticing the changes in the Source panel. Also, ifyoure curious about assembly language and register-level debugging, notice thechanges in the Assembly and Register panels.

6. Press Shift + F11 to step out of the current function (MCU_init) and back to thecalling function (main).

7. If the Data:2 panel in the lower left is not currently displaying the LoopCountvariable, right click anywhere in that panel, select Add Expression, and enterLoopCount. Spell it exactly that way since C is case sensitive. The new variableshould then display in the Data:2 panel.

8. Press the F5 button to put the uC into Run mode rather than single step mode.The LoopCount value may or may not be visibly changing, depending on howyour PC is set up. This value is actually changing constantly, but the debuggersdefault setting is to update the displayed value of the variable only when theprogram stops. Verify by watching the LoopCount value and pressing F5, F6, F5,F6 a few times to start and stop the uC. Verify that the toolbar Run button (greenright arrow) is changing colors as you go from Run mode to Stop mode.

9. If the uC program is not running, press F5 to start the execution again. Rightmouse click anywhere within the Data:2 panel and select Mode > Periodical,Rate: 1. This will update the displayed value every 100 mS.

10. In the Data:1 panel, change the Mode to Periodical with an update rate of 100 mS

using the same method as in the Data:2 panel.11. Expand the _PTAD and Bits areas in Data:1. Watch the PTAD1 line while

repeatedly pressing and releasing button SW0. Notice the value changing from 1to 0 and back again. Notice also that the number turns red briefly the first time ithas changed state since the last display update. This is a nice feature. Also watchthe PTAD4 entry and notice that it is changing to match the state of LED1.

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Using Breakpoints

1. Press F6 to stop the uC program execution, and then press Ctrl+R to reset thetarget (the development board).

2. If the Source panel is not currently displaying the main.c file, right click thatpanel and select Open Source File, main.c, OK.

3. Locate the text LoopCount < 32767; and right click anywhere on it, then selectSet Breakpoint. A red breakpoint symbol should appear to the left of thatprogram code.

4. Press F5 to run the program and notice that the lower right Command panelindicates STARTED RUNNING Breakpoint. F5 started the program, it wasrunning, and then it encountered a breakpoint and stopped. The Source andAssembly panels indicate the stop point: right at the breakpoint we just set, whichis in the middle of a for instruction that is looping and incrementing LoopCount.

5. Notice the value of the LoopCount variable in the Data:2 panel. Press F11

repeatedly and watch the value increasing. If the value does not change, verifythat you still have the update mode set correctly (right mouse click anywherewithin the Data:2 panel and select Mode > Periodical, Rate: 1).

6. Optional: If you are curious about the assembly language code, watch theAssembly panel while repeatedly pressing Ctrl+F11 to step through eachassembly language instruction. Also, check out the right click options in theAssembly panel.

7. Youve just used an unconditionalbreakpoint. Now well set a conditionalbreakpoint. Ctrl+R to reset the uC again, then open main.c in the Source panel.Right click anywhere in Source and select Show Breakpoints. This will open awindow in which you can set certain conditions that must be satisfied before the

breakpoint will cause the program to break. In the Condition field, enter thecondition LoopCount==14 (this says break at this point when LoopCount isequal to 14). Click OK, OK.

8. Press F5 to Run and watch the Source, Data:2, and Command panels.

There are a number of other very nice features in the debugger tool that you may wish toexplore and learn on your own. Have fun!

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Stand-alone uC Circuit Example:Minimum Circuit Required for the Hello World Example Program

Here is the minimum circuit required for running the Hello World program with a stand-alone RS08 microcontroller:

If one were to breadboard and test the above circuit, they would have to keep in mind thefollowing key points:

1. Input PTA1 MUST be set to pullup. This would be done by using the DeviceInitialization tool mentioned in the beginning of this lab.

2. Capacitor C1 may not be required in all situations, but the uC may not go intoRun mode without it. More information about operating modes may be found inthe uC data sheet.

3. R1 is sized to limit PTA4 current to a level that will not overload and damage theuC chip. Do not change the value of R1.

4. It would make sense to develop and test the program on the demo board first.You would not have the option to test and debug while it is plugged into thebreadboard. It is possible to connect to the uC for debugging, but that connectionis beyond the scope of this lab.

5. Care should be exercised when removing the uC chip from the demo board andbreadboard since the pins are very delicate, plus the chips are static sensitive.

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Links to Executable Programming Examples Provided with thisTraining Material (CD or unzipped directory)

Place the RS08 chip back into the demo board and go through the following examples asyou desire.

1. Keyboard Interrupt with STOP (low power mode) Instruction contains C andAssembly mixedThis program demonstrates the use of low power stop mode and keyboardinterrupts, the latter of which basically allows the chip to detect active inputsignals.Open the device initialization tool and notice that some of the blocks are aqua,indicating that they have been changed from their original settings. Specifically,the COP feature is turned off, keyboard interrupt requests are enabled, and theKBIP1 feature is set active for pin 7 to detect low or falling edges. With thissetup, any time pin 7 is pulled low by external circuitry (SW0 on the demo

board), a keyboard interrupt is generated. Hold that thought.The first thing done is the main function is that the uC is put into low power stopmode. This may be useful for applications where power consumption must beminimized, such as battery powered systems. The uC will stay in stop mode untilSW0 is pressed, at which time a keyboard interrupt is generated (because theKBIP1 input is seen going low) and the uC is automatically taken out of stopmode and into run mode. The uC then continues running the program after theSTOP command, toggling the output connected to LED1, acknowledging theinterrupt, and then going into stop mode again.

2. Boolean Logic DemoIn this program example, some simple Boolean logic is demonstrated (NOR,

AND, OR functions, etc.). Also, parameter passing with a function isdemonstrated in the NOR function. Nothing fancy is happening with the deviceinitialization.

3. Chasing Lights Pulse Width Modulation (PWM) DemoThis demo uses the built-in timer module to generate a 34 uS timebase. SeeMTIM settings in Device Initialization. Also, KBIP1 is set up again to monitorthe input tied to SW0. This program makes plentiful use of functions andparameter passing to alternately dim and brighten the lights. This dimming effectis accomplished through PWM, which basically blinks the LEDs very fast andcontrols apparent brightness by varying the duty cycle (percentage of entire cycleduring which LED is on as compared to off).

Pay special attention to the following lines in which the program waits until thenext 34 uS time tick:

while( ! SIP1_MTIM); // wait for overflow interrupt flag from timerMTIMSC_TRST = 1; // reset timer and acknowledge the interrupt

Also pay attention to this code, which checks to see if the user has pressed theinput button recently:// look for user-requested cycle change

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http://opt/scribd/conversion/tmp/scratch6661/Projects/STOP_KBI_Example/STOP_KBI_Example.mcphttp://opt/scribd/conversion/tmp/scratch6661/Projects/STOP_KBI_Example/STOP_KBI_Example.mcphttp://opt/scribd/conversion/tmp/scratch6661/Projects/Logic%20Demo/Logic%20Demo.mcphttp://opt/scribd/conversion/tmp/scratch6661/Projects/Chasing%20Lights%20PWM%20Demo/Chasing%20Lights%20PWM%20Demo.mcphttp://opt/scribd/conversion/tmp/scratch6661/Projects/STOP_KBI_Example/STOP_KBI_Example.mcphttp://opt/scribd/conversion/tmp/scratch6661/Projects/STOP_KBI_Example/STOP_KBI_Example.mcphttp://opt/scribd/conversion/tmp/scratch6661/Projects/Logic%20Demo/Logic%20Demo.mcphttp://opt/scribd/conversion/tmp/scratch6661/Projects/Chasing%20Lights%20PWM%20Demo/Chasing%20Lights%20PWM%20Demo.mcp


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if(SIP1_KBI) {

4. Array Size TestingThis example shows how to work with multi-dimensional arrays, a powerful andcommonly used C construct.In addition, it demonstrates something called compiler directives thecommands beginning with a # sign. If you do not understand these commands,ask your lab instructor to clarify.Finally, the program shows how to determine uC memory usage and how constantarrays and variable arrays are stored in different memory areas. This could beuseful to know when conserving memory is important. Read and follow thecomment instructions provided in the program.

5. Enumeration DemoThis program shows several examples of enumeration, which is a programmingtechnique for assigning integer values to some words such as LED names &statuses and musical notes. Since there is no speaker attached, you cannot hear

the musical notes.6. Comparator Demo

This program will not work with the demo board because there is no variableanalog voltage present. However, following the device initialization and programlogic demonstrates how the analog input comparator could be used. Note thatSIP1_ACMP is a bit that gets set when the analog compare condition is true,that is, the positive compare input is greater than the negative compare input.

7. Real Time Clock (RTC) Interrupt DemoLook at the device initialization and main function to see how real time clockinterrupts are used. Basically, a clock on the uC running in the background setsbit SIP1_RTI high every 131.072 mS. This is used to blink LED3

approximately once per second and LED2 approximately 8 times per second.

51507548.doc Page 34 of 35
http://opt/scribd/conversion/tmp/scratch6661/Projects/Array%20Size%20Testing/Array%20Size%20Testing.mcphttp://opt/scribd/conversion/tmp/scratch6661/Projects/Enumeration%20Demo/Enumeration%20Demo.mcphttp://opt/scribd/conversion/tmp/scratch6661/Projects/Comparator%20Demo/Comparator%20Demo.mcphttp://opt/scribd/conversion/tmp/scratch6661/Projects/RTC%20Interrupt%20Demo/RTC%20Interrupt%20Demo.mcphttp://opt/scribd/conversion/tmp/scratch6661/Projects/Array%20Size%20Testing/Array%20Size%20Testing.mcphttp://opt/scribd/conversion/tmp/scratch6661/Projects/Enumeration%20Demo/Enumeration%20Demo.mcphttp://opt/scribd/conversion/tmp/scratch6661/Projects/Comparator%20Demo/Comparator%20Demo.mcphttp://opt/scribd/conversion/tmp/scratch6661/Projects/RTC%20Interrupt%20Demo/RTC%20Interrupt%20Demo.mcp


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Additional Resources

Documents Provided with this Training Material (CD or unzippeddirectory)

Freescale RS08-related:

DEMO9RS08KA2 Development Board Users ManualDEMO9RS08KA2 Development Board SchematicRS08KA1 & KA2 Microcontroller Data SheetRS08 Core Reference Manual (assembly language instruction set, etc.)RS08 Assembly Language Demos & Quick Reference User's GuideApplication Note on RS Data Structures (not too intense)

C Language-related:

Freescales Learn_Programming_with_C

C Language Keywords: C Language Keywords.mht

Online Resources

Review of bits, bytes, etc.: http://www.learn-c.com/data_lines.htmTutorial on C programming with microcontrollers: http://www.learn-c.com/alltoget.htmOnline C language reference: http://ccs.ucsd.edu/c/C Programming:

http://www.imada.sdu.dk/~svalle/courses/dm14-2005/mirror/c/ccourse.htmlC Language FAQs: http://c-faq.com/index.htmlDeveloping Embedded Software in C:

http://users.ece.utexas.edu/~valvano/embed/toc1.htmThe GNU C Library - Table of Contents :

http://www.ia.pw.edu.pl/~wujek/dokumentacja/gnu/libc/libc_toc.htmlC Reference, Searchable and quite good: http://www.sysprog.net/cplus.htmlFree IDE/C compiler for the mid-to-low end Freescale microcontrollers:

www.freescale.comand search for CWX-HC08-SE

Support

CodeWarrior website: www.freescale.com/codewarriorCodeWarrior email support: [email protected]

General support for entire Freescale product line: www.freescale.com/support

Purchasing Your Own Demo Kits and Microcontrollers

Various vendors sell microcontrollers and demo kits. The best price ($10 + S&H) for theDEMO9RS08KA2 may be found here:

www.avnet.com and search for DEMO9RS08KA2.
http://opt/scribd/conversion/tmp/scratch6661/demo9rs08ka2_manual.pdfhttp://opt/scribd/conversion/tmp/scratch6661/demo9rs08ka2_schematic.pdfhttp://opt/scribd/conversion/tmp/scratch6661/MC9RS08KA2%20&%20KA1%20Data%20Sheet.pdfhttp://opt/scribd/conversion/tmp/scratch6661/RS08RM.pdfhttp://opt/scribd/conversion/tmp/scratch6661/RS08%20Demos%20&%20Quick%20Ref%20User's%20Guide.pdfhttp://opt/scribd/conversion/tmp/scratch6661/RS08%20Data%20Structures%20-%20AN3334.pdfhttp://opt/scribd/conversion/tmp/scratch6661/Learn_Programming_with_C.pdfhttp://opt/scribd/conversion/tmp/scratch6661/C%20Language%20Keywords.mhthttp://www.learn-c.com/data_lines.htmhttp://www.learn-c.com/alltoget.htmhttp://ccs.ucsd.edu/c/http://www.imada.sdu.dk/~svalle/courses/dm14-2005/mirror/c/ccourse.html%20http://c-faq.com/index.htmlhttp://users.ece.utexas.edu/~valvano/embed/toc1.htmhttp://www.ia.pw.edu.pl/~wujek/dokumentacja/gnu/libc/libc_toc.htmlhttp://www.sysprog.net/cplus.htmlhttp://www.freescale.com/http://www.freescale.com/http://www.freescale.com/codewarriormailto:[email protected]://www.freescale.com/supporthttp://www.avnet.com/http://opt/scribd/conversion/tmp/scratch6661/demo9rs08ka2_manual.pdfhttp://opt/scribd/conversion/tmp/scratch6661/demo9rs08ka2_schematic.pdfhttp://opt/scribd/conversion/tmp/scratch6661/MC9RS08KA2%20&%20KA1%20Data%20Sheet.pdfhttp://opt/scribd/conversion/tmp/scratch6661/RS08RM.pdfhttp://opt/scribd/conversion/tmp/scratch6661/RS08%20Demos%20&%20Quick%20Ref%20User's%20Guide.pdfhttp://opt/scribd/conversion/tmp/scratch6661/RS08%20Data%20Structures%20-%20AN3334.pdfhttp://opt/scribd/conversion/tmp/scratch6661/Learn_Programming_with_C.pdfhttp://opt/scribd/conversion/tmp/scratch6661/C%20Language%20Keywords.mhthttp://www.learn-c.com/data_lines.htmhttp://www.learn-c.com/alltoget.htmhttp://ccs.ucsd.edu/c/http://www.imada.sdu.dk/~svalle/courses/dm14-2005/mirror/c/ccourse.html%20http://c-faq.com/index.htmlhttp://users.ece.utexas.edu/~valvano/embed/toc1.htmhttp://www.ia.pw.edu.pl/~wujek/dokumentacja/gnu/libc/libc_toc.htmlhttp://www.sysprog.net/cplus.htmlhttp://www.freescale.com/http://www.freescale.com/codewarriormailto:[email protected]://www.freescale.com/supporthttp://www.avnet.com/

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