How to achieve a freeze of certain logic states?

Ruebezahl

Hello,

I have a question, that i am actually sure there is a simple answer, because it seems like a very essential function, but perhaps i just don't know how to desribe what i want the proper way, so search engines didn't yield the wanted results so far.

Well basically what i have is a CD4089, which four logic inputs A, B, C, and D i control through pushbutton, so the divisions are based on what combination of pushbuttons i press at a time. Nothing complicated.

What i want: I would like to be able to kind of freeze whatever combination i am pressing at a time, by means of another switch. So for example if at a certain time i press pushbutton A and pushbutton B, and i press said switch, the logic inputs of the 4089 will receive the same combination of 1 and 0, even if i release the pushbuttons.

I stumbled across JK flip flops, but they both are a bit complicated to build (i'd prefer a single chip solution) and i think i can still not wrap my head around how they work and if that's what i need. I somebody says "yeah that's it" i will promise to do my homework and read up on those, but otherwise i though i'll try asking first before spending a lot of time trying to understand something that's not really solving my problem Wink

Thanks a bunch!

elektrouwe · Joined: May 27, 2012 Posts: 146 Location: Germany

Ruebezahl · Posted: Fri Apr 22, 2022 12:48 am Post subject:

Thank you! That seems exactly like what i need Smile

PHOBoS · Posted: Fri Apr 22, 2022 6:09 am Post subject:

also look into what is called a "transparent latch'

Ruebezahl · Posted: Sun May 01, 2022 11:02 am Post subject:

That sounds actually even more than what i want, since it is actually just passing through until it is triggered. However, in my short search i saw only a handful of cmos chips (MC74LCX373) that do that, and their power limits were super narrow for cmos, 2.3v to 3.6v.

Would you have any particular chip in mind, especially one that would run off a 9V battery? (well obviously you can use voage regulators, but then i also have to interface the signals from the other chips, which makes everything a bit more complicated than i would like it to be)

Actually i already picked up a 40175 recently, so i will try that one first, but for future endeavors would be nice to know.