1
\$\begingroup\$

I use EveryCircuit as a simple circuit simulator. For my very novice-level fumblings it has served me well. I have been using this chip, which is called Counter IC. It has 4 output pins A-D, which count up from 0 to 15 in binary. I figured out how to use the up, down, carry, borrow, and reset pins. I am confused about the pins on the left, however. The pins labeled 1, 2, 4, and 8 don't seem to do anything at all, and neither does load.

Is this counter based on an actual IC that I could look up? I tried looking at datasheets for some counter ics but they didn't match up with this.

Also, what function do the pins on the left side of this chip serve?

enter image description here

\$\endgroup\$
2
  • \$\begingroup\$ (what function do the pins on the left side of this chip serve? educated guess: 1-8 preset the counter on load.) \$\endgroup\$
    – greybeard
    Dec 7, 2022 at 17:41
  • \$\begingroup\$ The counter will default to counting up from 0 to 15 (and wrap back to 0 and continue), or down from 15 to 0 (and wrap back to 15). If you’d rather say, count down from 6 to 0 then you would encode “6” onto the input pins (1-2-4-8) and assert LOAD (high, presumably). This forces outputs immediately to 6, then count down continues to zero, but will then wrap to 15. So if you want it to count from 6 again you have to devise a circuit that detects reaching zero and use that to re-LOAD 6 again. \$\endgroup\$
    – td127
    Dec 7, 2022 at 23:23

1 Answer 1

2
\$\begingroup\$

The pins named '1', '2', '4', '8' are the value to asynchronously load into the counter when 'load' is asserted.

Their names are the component values of a binary number from 0000b..1111b, or 0..15 decimal. Those value pins would more conventionally be named 'D0', 'D1', 'D2', 'D3' for 'data' but could be something else.

The circuit shown is not a 74191 but it's not that far from it, as the below diagram from its datasheet shows. That uses some different pin function though, including a parallel load /PL, a clock pulse input CP and a 'down, not-up' count direction control /U D.

enter image description here

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.