How do I start?

A good place to start would be Microchip's web site,

There you will find data sheets and other useful information. You will need some sort of programmer to read out the code from the chip, and after you do, it's not likely to make a lot of sense. Going from hex code to understandable english won't be easy, and you will need the data sheets to tell instructions from interrupt vectors using the addresses and other info contained in the data sheets.

Hello Tom,

Thank you very much for your answer. I already found the data on

I also found several programmers and software. Most of the programmers can be used for a lot of IC's. I also found several programs fot pc (sometimes in combination with the hardware like GALEP4) I once did a course about microprocessors, how they exactly work in machine code. That where the Intel 8080, Z80 the 6800 and 6502. So I'm al little bit familiar with it. But I understand that you have to make a program in a higher level language? most easy for me is basic I guess, though I did a little Pascal programming.

So the questions I have is, what programmer do you suggest, which program on my pc, and how do I write a simple program, in what language or instructions.

My goal is to understand how my central heat unit works, what program is behind it. I know it starts with, leak check, ventilation of the boiler, ignition, test if there is ignition fire, open the main gas valve....

I also read something about protection of the program, that that is possible with the 16F870. I can imagine that programmers want to protect their program ofcourse.

Thank you for answer and advice.

Wim

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I would recommend the EasyPic3 from Mikroelectronica. For $169 you get a board with loads of peripherals, code limited C, Pascal and Basic compilers, the latest MPLAB IDE from microchip. With this you could very likely duplicate most if not all of your furnace functions. Yes, there is a code protection switch in the chip, set it during programming and the chip can not be read, only erased.

You might also want to look at ComFileTech's Cublock starter systems, they're reasonably priced and use a combination of basic and "ladder Logic", they are much better suited to industrial or furnace control, as you deal directly with relays, switches and conditions. Based on an Atmel chip, but the language is not specific, and it's sort of basic stamp 2 compatable.

Hope I haven't confused you too much.