What is always the most difficult thing to do? You have bought the microcontroller, you have learned everything about its circuits and registers, you have a great idea how to apply all your knowledge in practice. But the most difficult thing to do is to start...

How to start working?

A microcontroller is a good-natured “genie in the bottle” and no extra knowledge is required to use it. In order to create a device controlled by the microcontroller, it is necessary to provide the simplest PC, program for compiling and simple device to transfer the code from PC to the chip itself. Even though the whole process is quite logical, there are often some queries, not because it is complicated, but for numerous variations. Let’s take a look.

Writing program in assembly language

In order to write a program for the microcontroller, a specialized program in the Windows environment may be used. It may, but it does not have to... When using such a software, there are numerous tools which facilitate the operation (simulator tool comes first), which is an obvious advantage. But there is also another ways to write a program. Basically, text is the only thing that matters. Any program for text processing can be used for this purpose. The point is to write all instructions in such an order they should be executed by the microcontroller, observe the rules of assembly language and write instructions exactly as they are defined. In other words, you just have to follow the program idea. That’s all!

;RESET    VECTOR
          CSEG    AT      0
          JMP     XRESET           ; Reset vector

          CSEG
          ORG     100H

XRESET:   ORL     WMCON,#PERIOD    ; Define Watch-dog period
          ORL     WMCON,#WDTEN     ; Watch-dog timer is enabled

To enable the compiler to operate successfully, it is necessary that a document containing this program has the extension, .asm in its name, for example: Program asm. When a specialized program (mplab) is used, this extension will be automatically added. If any other program for text processing (Notepad) is used then the document should be saved and renamed. For example: Program.txt -> Program.asm. This procedure is not necessarily performed. The document may be saved in original format while its text may be copied to the programmer for further use.

Compiling a program

The microcontroller “does not undrestand” assembly language as such. That is why it is necessary to compile the program into machine language. It is more than simple when a specialized program (mplab) is used because a compiler is a part of the software. Just one click on the appropriate icon solves the problem and a new document with .hex extension appears. It is actually the same program, only compiled into machine language which the microcontroller perfectly understands. Such documentation is commonly named “hex code” and seemingly represents a meaningless sequence of numbers in hexadecimal number system.

:03000000020100FA1001000075813F
7590FFB29012010D80F97A1479D40
90110003278589EAF3698E8EB25B
A585FEA2569AD96E6D8FED9FAD
AF6DD00000001FF255AFED589EA
F3698E8EB25BA585FEA2569AD96
DAC59700D00000278E6D8FED9FA
DAF6DD00000001FF255AFED8FED
9FADAF6DD000F7590FFB29013278
E6D8FED9FADAF6DD00000001FF2
55AFED589EAF3698E8EB25BA585
FEA2569AD96DAC59D9FADAF6D
D00000001FF255AFED8FED9FADA
F6DD000F7590FFB29013278E6D82
78E6D8FED9FA589EAF3698E8EB2
5BA585FEA2569AD96DAF6DD000
00001FF2DAF6DD00000001FF255A
ADAF6DD00000001FF255AFED8FE
D9FA

In the event that other software for program writing in assembly language is used, a special software for compiling the program must be installed and used as follows - set up the compiler, open the document with .asm extension and compile. The result is the same- a new document with extension .hex. The only problem now is that it is stored in your PC.

Programming a microcontroller

In order to transfer a “hex code” to the microcontroller, it is necessary to provide a cable for serial communication and a special device, called programmer, with software. There are several ways to do it. A large number of programs and electronic circuits having this purpose can be found on the Internet. Do as follows: open hex code document, set a few parameters and click the icon for compiling. After a while, a sequence of zeros and ones will be programmed into the microcontroller through the serial connection cable and programmer hardware. What's left is to place the programmed chip into the taget device. In the event that it is necessary to make some changes in the program, the previous procedure may be repeated an unlimited number of times.

The end or...?

This section briefly describes the use of MPLAB and programmer software developed by Mikroelektronika. Everything is very simple... The program is written and successfully compiled. All that's left is to dump the program to the microcontroller. For this purpose it is necessary to have a software that takes the written and compiled program and passes it to the microcontroller. Start the program 8051 Flash_setup.exe... The program has been installed and ready for use. The settings are easily performed so that there is no need for additional explanations (the type of the microcontroller, frequency and clock oscillator etc.).

• Connect the PC and programmer via a USB cable;
• Load the HEX code using command: File -> Load HEX; and
• Click the 'Write' push button and wait...

Development systems