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Personal Computer Debugging Tool

geneb said:
http://www.retroarchive.org/dos/utils/pcdt.zip
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I have downloaded it and tried to disassemble the ROM. "Tried" because there is something that makes it hard to disassemble the code. But I think I already have the idea what the ROM does: what ever action is executed, the code for it has to be transferred from the PC acting as terminal. My reasoning: only 6 KB of the ROM is used and about 2 KB is text. OK, a good programmer can do a lot with 4 KB but being able to put all those tests described in the PDF plus all the routines needed to handle the COM port in these meager 4 KB? I have my doubts.

I wonder why they put all this text into the ROM? Just let the ROM handle the basic operations like loading a program and executing it IMHO. You can start with a small program that tests the memory in the first place. Then use the good memory to load other programs and their texts. Sounds like a nice project but I want to finish my Diagnostic ROM first.
 
geneb said:
http://www.retroarchive.org/dos/utils/pcdt.zip

This is a tool for working on PCs that have hardware faults. The software is on a replacement ROM and you can interact with it via a serial port on COM1. The zip file includes the ROM image as well as the contents of the disk that were included with the ROM.

Enjoy!

g.
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I have been asking for something like this for a long time. What is the deal with special serial card? Is it just a serial card with the EPROM on it or does it also have diagnostic functions?
 
Shadow Lord said:
I have been asking for something like this for a long time.
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That is something I realized later. I always thought you wanted the Diagnostic ROM as is PLUS serial support. The above idea has its advantages and disadvantages.

The biggest advantage: during the development of your tools you don't have to erase and burn so many times the EPROMs. In those days it mattered, I know from experience. EEPROMs solved that problem.

The disadvantage: you needed a second PC. I don't think that that is a problem either nowadays, certainly for members of this forum.

But having that second PC doesn't solve all problems. You need a program to talk with the PC-under-test. PCDT even provided the sources of a small terminal program. So far I run all self written programs that use the LPT and/or COM under DOS. This is because I only use them in combination with my various Commodores and some of these machines are so timing critical that XP+ or Linux are out of the question. (I know about CBM4WIN)
One solution is to find out if it is possible to write your own terminal program using Free Pascal or Lazarus (a Delphi clone). I'll ask on the forums there. But ideas from your site are welcome!

And why not using a standard terminal program? (IIRC that was suggested somewhere in the documentation of PCDT?) I know it is possible to download a file fro or to upload one to another PC, I did that two years ago using Kermit. First upload a program that will test some memory which on its turn will be used for a program that does the "talking" and provides the handles for the other tests.

But unfortunately this idea has to wait. I still want to finish my Diagnostic ROM first. Due to personal circumstances I wasn't being to work on it last months. But any ideas or comments are welcome!
 
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