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RS-232 and Frequency

Discussion in 'Electronic Design' started by Yin99, Jan 5, 2006.

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  1. Yin99

    Yin99 Guest

    If I have to provide a signal through a PC RS-232 port at 15 Hz using
    38400 baud, is this possible? What is the max frequency I could
    support? How would one calculate (derive) these answers?

    I know frequency = event / time unit. So 15 Hz is 15 times a second.
    This seems simple if you are talking about "event" being a simple
    binary 1 (logic high). That would read "how many times you can pulse a
    1 every second". But what if the "event" is a stream of 170 bits?
    Does that effect the questions above? Note: I am talking about PC <->
    PC RS-232 communications (not using a modem). Thanks,

    yin99
     
  2. Joel Kolstad

    Joel Kolstad Guest

    Come on, surely this is a homework question, right?

    First, realize that with RS-232 "baud"="bits per second". So you can send
    38,400 bits per second... you want to send an "event" consisting of 170 bits
    at 15HZ, so that's 170*15=10,650 bits per second -- clearly this will fit
    through a 38,400 bps 'pipe.'

    This does get trivially tricker in that usually one speaks of sending a byte
    from their PC and this takes more than 8 bits over RS-232 since you have to
    add at least a start and stop bit (and may add more... parity, longer stop
    bits, etc.) -- hence requiring at least 10 RS-232 bits to send one byte of
    data -- but since you question doesn't mention this, I'm assuming it's
    immaterial.
     
  3. Guest

    On a side note, this is one of the reason I like to use the 8N1 for mat
    so much. It's 10 bits per byte. 38400 baud? Why, that's 3840 kB/s!
     
  4. Guest

    On a side note, this is one of the reason I like to use the 8N1 for mat
    so much. It's 10 bits per byte. 38400 baud? Why, that's 3840 kB/s!
     
  5. budgie

    budgie Guest

    it walks like a duck, it looks like a duck, it sounds like a duck .....

    Of course the O/P could simply toggle a handshake line ....
     
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