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74HC390 table of pin connections?

Discussion in 'General Electronics Discussion' started by Gillie, Apr 14, 2017.

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  1. Gillie

    Gillie

    13
    1
    Apr 14, 2017
    Hello

    First question here. I want to experiment with 74HC390 chip. I know the pin strappings for divide by 4 (example (14 to 2), (15 to 3), (2,4,8,12,14 to Ground), 1 in and 13 out) and divide by 100 from a Mr Carlson's Lab YouTube clip, but I would like to find the pin strappings for the other possibilities (I believe I could divide by 2,5,10,20,25,50?). Someone must have produced a table, but extensive Googling fails to find it!
     
  2. Audioguru

    Audioguru

    3,136
    698
    Sep 24, 2016
    Did you look at the datasheet of the SN74HC390? Oh, Texas Instruments say it is obsolete do not show its datasheet.
     
  3. Gillie

    Gillie

    13
    1
    Apr 14, 2017
    Thanks for the speedy reply! Unfortunately, I cannot glean the info I need from the datasheets.
     
  4. hevans1944

    hevans1944 Hop - AC8NS

    4,595
    2,149
    Jun 21, 2012
    Well, actually you can if you understand how the counters work. Review this Texas Instruments datasheet for this obsolete and no longer manufactured part. Then breadboard a trial circuit using a low-speed clock, typically a de-bounced push-button switch, and a logic probe to see what is going on.
     
  5. Herschel Peeler

    Herschel Peeler

    401
    65
    Feb 21, 2016
    See attached pdf.
     

    Attached Files:

  6. Herschel Peeler

    Herschel Peeler

    401
    65
    Feb 21, 2016
    OOPs! After looking at it the Divide by 25 doesn't work. I will have to reconsider that.
     
  7. Herschel Peeler

    Herschel Peeler

    401
    65
    Feb 21, 2016
    Divide by 25 reconsidered.
     

    Attached Files:

    hevans1944 likes this.
  8. Herschel Peeler

    Herschel Peeler

    401
    65
    Feb 21, 2016
    Even simpler. Five fives. One last time.
     

    Attached Files:

  9. Herschel Peeler

    Herschel Peeler

    401
    65
    Feb 21, 2016
    The 74xx390 is two divide-by-ten counters. Each section has a divide-by-two and a divide-by-five part. So all you have to do is break down the count you want (in your case) into 2's, 5's, and 10's and use the sections as they are designed. Take another look at the data sheet, more closely this time.
    Divide-by-two uses one divide-by-two section of one counter. Divide-by-five uses one divide-by-five section of a counter. Divide-by-ten just tie one divide-by-two to one divide-by-five and you have a divide-by-ten. It doesn't matter which you do first.. Divide-by-twenty, is a divide-by-ten and a divide-by-two. It doesn't matter which you do first. Divide-by-twenty-five is two divide-by-fives. Divide by fifty is a divide-by-five and a divide-by-ten. It doesn't matter which you do first.-
    For counts other than something divisible by 2 or 5 you need to use a AND gate and take the high outputs of one of the divide-by-five sections. Straight binary stuff. (Learn binary.)
     
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