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Thread: TTL SIgnals - Pins?

  1. #1
    Join Date
    Feb 2012
    Posts
    4

    TTL SIgnals - Pins?

    Hello, the docs say that DirectRT can send TTL signals through a PC port, but I can't seem to find any reference as to which pins on the port carry the TTL signal. I need this information in order to build a custom electrical circuit that would receive these signals. Any help will be appreciated.

  2. #2
    Join Date
    Nov 2005
    Posts
    294
    I'd refer you to this excellent overview:

    http://retired.beyondlogic.org/spp/parallel.htm

    Summary: pins 2-9 are the data bus output. Pins 18-25 (inclusive) are ground.

    And also double-remember that these signals are quite weakly buffered. Add some current limiting resistors, and watch out for accidental short circuits.

  3. #3
    Join Date
    Feb 2012
    Posts
    4
    Thank you, much appreciated.

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