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31070Re: CP/M CBIOS LST question

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  • joshbensadon
    Jun 1, 2013
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      --- In midatlanticretro@yahoogroups.com, Richard Cini <rich.cini@...> wrote:
      >
      > All --
      >
      > I solved the printing problem and now have a working modem and printer for
      > my IMSAI.
      >
      > ...
      > NULL modem adapter to the serial input cable. Two NULLs makes, well, no
      > NULL. Straight through is the key, and I needed to change the jumper on the
      > Interfacer.


      Well done Rich!

      I save a lot of time with RS-232 by using an LED Tester. It has male & female DB connectors and plugs in line to show which lines are being driven. Connect it to one side first and observe the TX led is on, then unplug and connect to the other side and observe the RX led is on. If both show TX (or RX) led's on, then you need a NULL (or undo a NULL?).

      I highly recommend you get an 18 LED tester. There are some 9 LED testers that use bi-colour LED's. These suck as you can't see the data pulses unless you have a very keen eye for colour changes (which I don't). The 18 LED tester uses 2 LED's for each line so even at the fastest baud rates, you can easily see a dim glow.

      Here are some links:

      http://www.amazon.com/DB25-Male-Female-Check-Tester-LEDs/dp/B000I96BB0
      $7.65


      http://www.cablesonline.com/rsdbmf18ledm.html
      $6.99

      :)J
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