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Thread: Multicomp z80 rom-mjs - changing baud rate?

  1. #1

    Default Multicomp z80 rom-mjs - changing baud rate?

    Does anyone know how to change the default baud rate from 9600 to 115200 on cycloneiic-z80 running cp/m 2 with rom-mjs?
    I don't know where these settings are defined, perhaps the multicomp build? or in the rom monitor or cp/m bios ? I've not found the sources of monitor or cbios to check, but if someone knows the location I could patch?

    Ideally I'd love to have the sources to make changes more manageable, but patching is fine.


  2. #2


    Not sure about ROM-MJS but on a standard Multicomp, the baud rate is set in the Microcomputer.vhd file at the bottom.

    -- Serial clock DDS
    -- 50MHz master input clock:
    -- Baud Increment
    -- 115200 2416
    -- 38400 805
    -- 19200 403
    -- 9600 201
    -- 4800 101
    -- 2400 50
    serialClkCount <= serialClkCount + 2416;
    The value you add to serialClkCount determines the baud rate - in this example it is set to 115200.

  3. #3


    Thank you, I've just tried that and the baud rate is working at the higher speed, though doing [return key] multiple times at cp/m command prompt is not just giving me the command prompt, I am getting some miscellaneous characters so I need to move from Mac (Serial) to Windows (Teraterm) to see if the behaviour is consistent. Happens on cp/m2 and cp/m 3. Also I need to drop baud rate back and see if it is reproducible.

  4. #4


    What speed are you running it at?

  5. #5


    I am now successfully working at 115200 baud with rom-mjs multicomp. My problems of serial corruption were caused by an FTDI clone (didn't intend it to be a clone when I purchased from Amazon), problems went away when switching to genuine article. I had used the clone for many months on other systems without linking it to other problems, but it might be the source of some other problems I'd seen

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