? about electronic switching and CD4017

[gak]

hi guys
hey, i've been thinking about electronic switching and all that stuff... i'm trying to design something, but i have one question that i couldn't find out reading the datasheet...
does the CD4017 "remember" it's state when power supply is unlpugged? if it doesn't, is there some similar CMOS IC or something ( ?) capable to do that?  :?:

[R.G.]

No CMOS switch remembers its state when power goes off.

You can make this almost not matter by providing a battery back up for the memory elements when main power is off. CMOS is a natural for this.

[gak]

that's a good idea, i didn't think about that

how should i do that? should i provide a different power supply for the CMOS than the one used by the rest of the circuit all the time? switch to another supply when turned off? ..?

[Peter Snowberg]

You can power the flip-flip part of the switching circuit from two places at once by using two diodes. Connect one diode to each source of power with the sides with the bands connected together and pointing toward the flip-flip. Any diode should work fine but the most preferred ones would probably be schottky diodes like the 1N5818. Use a 1N4001 or 1N914, either will be just fine.