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Thread: Cbm-ii rs232c

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    Post Cbm-ii rs232c

    I seem to have forgotten most of what I know about the CBM-II and seem to have lost any documentation I had.

    Does anyone know the memory location of the ACIA? Or better yet, have a full memory map? I'd like to use the RS232C port on my B128 from BASIC.

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    Quote Originally Posted by KC9UDX View Post
    I seem to have forgotten most of what I know about the CBM-II and seem to have lost any documentation I had.

    Does anyone know the memory location of the ACIA? Or better yet, have a full memory map? I'd like to use the RS232C port on my B128 from BASIC.
    I am sure there is a better resource, but I always go to this issue of Transactor for this sort of thing:

    https://archive.org/details/transact...v4-i05/page/n3

    Page 48-49.

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    Perfekt! Thank you!

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    Well, don't believe everything you read, especially in any documentation about Commodore 8-bits.

    In that table, DD02 and DD03 are swapped. The 6551 registers are the other way round. But at least the 6551 is actually at DD00.

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    This turned out to be an excersise in futility. There's no need to set up the chip manually in BASIC.

    The way to open the RS232 device is the same on the B128 as it is on the Vic-20 and C64. I don't know why I didn't expect Commodore to be so practical.

    OPEN1,2,3,"{control register}{command register}" is the proper way to initialise the chip. Note that on the other Commodore machines, a secondary address of 0 is used, but for some reason, 3 is necessary here.

    At least I have the information I'll need when I switch to assembly.

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    Quote Originally Posted by KC9UDX View Post
    Well, don't believe everything you read, especially in any documentation about Commodore 8-bits.

    In that table, DD02 and DD03 are swapped. The 6551 registers are the other way round. But at least the 6551 is actually at DD00.
    I went and checked my physical copy and I had noted on it that the registers were swapped. I knew that rang a bell as soon as you said it. Sorry if that delayed you too much.

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    Thanks; but it's my fault: I should've been following the datasheet that was in front of me in stead of that map. This isn't the first time I ran into something like this in Commodore 8-bit documentation. Really though it's a miracle we have as much information as we do.

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