Programming Intel 8085

[G2003]

Hello,

i have an older piece of proprietary cable equipment that i would like to reprogram. it uses the Intel 8085 processor. What all is needed to reprogram
the processor?

Thanks,
Gil

 

[Terry Yager]

Ummn, not enough information...

At a minimum you'll need I/O, some way to communicate with the controller, such as a terminal, etc (assuming that the device has some kind of serial port). My 8085-based SDK uses only a keypad and some 7-seg LEDs for I/O.

You'll also find it helpful to have some kind of storage device, and of course, a working knowlege of 8080/85 Assembly Language, or a higher-level language that outputs 8085-compatible code.

It's difficult to guess what all you'll need, but please do tell us more about the project.

--T

 

[SwedaGuy]

I'm working on a similar project right now...the brute force method worked best for us:

Yank out the ROMs, read them using a device programmer, save the file and have one of the commercially available disassemblers create source code for you. We used the 8085 simulator by Oshonsoft, (Very good, btw, if you don't object to the Windows interface) but free or inexpensive disassemblers are available on the net.

The disassembler will create a text file with the uncommented source code in it. I recommend importing that into your spreadsheet of choice, or if you have an assembly language IDE for the 8085 (I don't) that's even better. Having the source in a spreadsheet allows searching, search & replace, syntax highlighting, and a few other handy features.

If there is constant data embedded in the source code, you'll have to figure that out the hard way. I'll assume that you have at least a fundamental knowledge of the assembly language, so that if you see something like this:

mov a,b
mov a,d
mov a,e

in sequence, you know that it's not a valid sequence of instructions and is therefore probably constant data.

Do you have schematics for this unit? They can be invaluable in determining device I/O ports.

How drastic are the changes you are trying to make?

This may not be easy--we have a wealth of information available pertaining to the device we're working on, and I'm still more than a year into the project and only about 35% done. It's very tedious work. Of course we're commenting the entire source file, you may have a smaller project. The program I read out is 32K, which disassembled into just over 13,000 lines of code. Now that I've ironed out and expanded most of the constant data, added blank lines for readability and commented the code (remember I'm only about 35% done) I'm up to just over 20,000 lines in the source file.

Oh, and get yourself one of those calculators that does math in Hex and will perform base conversions...you'll need it.

I'll say this, too: for as slow and tedious as this process can be, it's really kind of exciting to see a section of code come together.