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Thread: vt420 gripes

  1. #11
    Join Date
    Mar 2017
    New Jersey, USA


    It's possible the VT420 might send ^S and ^Q when in PC TERM mode (in that mode it uses 0x65 and 0x67 for XON/XOFF), but I don't know if PC TERM mode will work without a PC keyboard attached, and even if it does work you will have to program your bridge to convert PC scan codes back to ASCII before forwarding keystrokes to the upstream host.

    It is sounding like more and more of a nuisance to make the VT420 do things it wasn't really designed for. It would be a lot simpler to just slow down the baud rate to something that the terminal can keep up with, even with flow control disabled. This is the reason I normally leave smooth scroll disabled -- it looks nice but it slows the terminal down too much and I'd rather have a higher baud rate than smooth scrolling. I think with smooth scrolling turned off, the terminal can run at 9600 baud without flow control and without dropping characters.

  2. #12


    Yeah, I don't want to convert those scan codes for sure. I'd rather just remap two keys to XON/XOFF if I had to. I wrote a win32 getch function a month or so ago that deal with converting scan codes and it was annoying to do.

    I was thinking the same thing about the 9600 baud, but apparently there are still things that can cause it to glitch. Probably asking it to clear to end of line or something. I couldn't get turbo pascal's tinst to not glitch even as low as 9600 baud. I too like the smooth scrolling, but I can't image how slow it would have to be to support it. I guess I'll find out if I get this bridge built - I should be able to turn it on and though it will be slower, there shouldn't be any data loss.

  3. #13
    Join Date
    Mar 2006
    Salt Lake City, UT, USA


    Quote Originally Posted by alank2 View Post
    Hi Pete - I agree - there is something special about Turbo Pascal. I started on it in high school and learned a lot with it.
    It's the ability to quickly iterate and try out code; it's the same reason people like interpreted languages like JS and Python now. It's very fast to quickly iterate on something to reach a final implementation.

  4. #14
    Join Date
    May 2018


    Anyone have the circuit diagram for the VT420 ?

    Managed to get one but the display was very dim and now I cant see it at all. The heater in the tube is glowing very faintly, so im suspecting somthing power related but would like any info I can get my hands on before I start real investigations.


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