Display while counting

[IvanStefanov]

It's like an automatic chronometer actually - a digital counter counts the time for the operation and shows it on the display. What I want is to make it display the result from the last count while counting.

 

[psurya1994]

Hi Ivan,
You can use a NOT logic, so if the forward counting is 0000,0001,0010,0011,.... the reverse counting would be 1111,1110,1101,1100.
The 74LS04 IC which has 6 NOT gates might help.

 

[IvanStefanov]

Thank you, Psurya! Problem is I am not sure how the NOT gates help me.

Let's say my counter reaches 0111 and I get a "7" on the screen. Then I reset the counter and it counts to 0100. While it counts the screen still shows "7", but when I'm to reset the counter again I get a "4" on the screen. How does inverting help me do that?
If I was in the university I would use a pic, but I can't get a pic and get it programmed before my deadline... I am sure there is a pretty simple solution like a lot of D triggers with a common clock

What I'm looking for is called Latch Driver ( 74hc4543 for example). Hope This post is useful to other people who have the issue.