I need a binary counter

Discussion in 'General Electronics Chat' started by pgo1, May 10, 2016.

  1. pgo1

    Thread Starter New Member

    Nov 7, 2012
    23
    0
    Im looking for a 3 bit (or 4 bit) synchronous binary counter with up/down counting, a synchronous load and an asynchronous clear.

    Failing that, the easiest way to fudge that from existing chips. Any ideas? I was so close with a SN74HC161N but then my spec changed and I needed to go up and down easily - I was looking at the SN74HC193 but from what I read in the datasheet the load isnt synchronous

    Before anyone says it, I have looked through a parts supplier but didn't find anything - this is possibly a case of wishful thinking that I missed something
     
  2. GopherT

    AAC Fanatic!

    Nov 23, 2012
    6,009
    3,764
    CD4510 should do what you want.
     
  3. pgo1

    Thread Starter New Member

    Nov 7, 2012
    23
    0
    Thanks GopherT! The CD4510 might be the best for what I want, except the load function is still asynchronous, is that correct?

    Ideally i was hoping for one with a synchronous load - I want a look ahead on the final count as i am resetting the counter at various states and ideally want a perfectly synchronous counter
     
  4. GopherT

    AAC Fanatic!

    Nov 23, 2012
    6,009
    3,764
    I can't imagine there is something you could dream up that this counter cannot do. Loading preset values is synchronous.

    image.jpg
     
  5. GopherT

    AAC Fanatic!

    Nov 23, 2012
    6,009
    3,764
    Please post exactly what you want to do. I'm sure there is an easy solution.
     
  6. dl324

    Distinguished Member

    Mar 30, 2015
    3,242
    619
    Load and reset on a CD4510 are asynchronous and it's a BCD counter, not binary.

    If you post more information on your application, someone might have ideas for making load synchronous. Doing it only on the edge transition of the clock could require a bit of glue logic.
     
  7. pgo1

    Thread Starter New Member

    Nov 7, 2012
    23
    0
    yes, it looked like it from the datasheet - not sure which datasheet you are looking at GopherT? The logic diagram on this one (http://www.ti.com/lit/ds/symlink/cd4510b.pdf) seems to show immediate transition at the rising edge of a signal on the preset enable

    Im trying to make a counter which is preset to count to either 2, 4, 6 or 8, forward or backward, over and over. It must provide as little as possible delay between states - and preferably there should be no time difference when resetting as to when there is a state change.

    Im a little pushed for space too, so although I could go down the road of extra logic, i might forego that for now and build something around a counter without a synchronous reset and see if the extra flake of time on the rest is really that problematic..

    aha! I found one - SN54ALS169B

    ...................no i didn't. doesn't have asynchronous reset
     
    Last edited by a moderator: Oct 27, 2016
  8. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,528
    1,248
    169 - synchronous load, no reset
    163 - synchronous load, synchronous reset

    ak
     
  9. dl324

    Distinguished Member

    Mar 30, 2015
    3,242
    619
    The TI datasheet seems to be a scan of the old RCA datasheet. The 1994 Motorola datasheet has more information (this wasn't included in the 1978 version).
    upload_2016-5-12_9-40-11.png
    The truth table clearly shows that Reset and Preset are both asynchronous. Without that information, you could look at the logic diagram and see that Reset or Preset will generate a clock and that Reset is actually implemented as a load of zero.
    upload_2016-5-12_9-42-2.png
    If you decide to pursue making load synchronous, post your schematic/block diagram so we can see how load is implemented and give suggestions.
     
    Last edited: May 12, 2016
Loading...