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Thread: Replacing the LOAD routine on a PET.. possible without ROM replacement?

  1. #1
    Join Date
    Apr 2011
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    San Francisco, CA
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    Default Replacing the LOAD routine on a PET.. possible without ROM replacement?

    Hi there,
    Messing around with some PET software development, and I would like to replace the LOAD routine with a custom ML routine located elsewhere in memory.
    I've done this on a C64, which was fairly straightforward since the LOAD routine address is located in RAM ($0330) and can be directly replaced.
    Looking at the PET memory map, I don't believe this is the case, and appears that the only vector to the routine is in ROM, $FFD5.
    Is it correct to say that it is not possible to redirect LOAD to another execution address without a replacement ROM?
    I can also use the USR command to run the custom routine, but would be nicer to have a direct LOAD replacement. Thanks for the help,
    - Mike

  2. #2
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    Apr 2011
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    I should say, the PET model I'm currently using for this is an 8032, but the question would apply to any PET model.

  3. #3

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    You will have to insert a wedge into the chrget routine so it is directed to your code to trap the basic commands.

    If you Turn to page 365 in the book “programming the PET/CBM by Raeto West” you will find example code.

    Google the book and you will find a digital copy on the net.

  4. #4
    Join Date
    Jun 2012
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    UK - Worcester
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    It can be done. See https://archive.org/details/The_Basi...oolkit_for_PET.

    I will have to try and replace the brain cells I lost 30 years ago when I looked into this myself for a robotics project I did at university.

    Dave

  5. #5
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    Thanks! I will try these out.

  6. #6

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    Here’s the direct link

    https://archive.org/details/Programm...aeto/page/n371



    Quote Originally Posted by AndyG View Post
    You will have to insert a wedge into the chrget routine so it is directed to your code to trap the basic commands.

    If you Turn to page 365 in the book “programming the PET/CBM by Raeto West” you will find example code.

    Google the book and you will find a digital copy on the net.

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