Program select with 74hc148n

Mcfly · Post by **Mcfly** » Wed May 29, 2013 8:05 am

Hi to all, I would like to know how to correctly hook up a 74HC148N to pins S0,S1 and S2. Do i need to put some pull down resistors or not? I see the FV1 dev board schematic and it was done with this method.
Thanks!

frank · Post by **frank** » Wed May 29, 2013 9:22 am

That method was used on the SKRM board example schematics, not the dev board. Since the '148 can drive high and low you probably don't need the pull-up resistors on S0, S1 and S2.

Mcfly · Post by **Mcfly** » Wed May 29, 2013 11:24 am

frank wrote:That method was used on the SKRM board example schematics, not the dev board. Since the '148 can drive high and low you probably don't need the pull-up resistors on S0, S1 and S2.

Frank, please correct me if i'm wrong, but i can see that R13,R14 and R15 are pull down resistors in the dev board:

http://www.spinsemi.com/Products/appnot ... VB_sch.pdf

I won't use an encoder, just the 148, my question is do i have to use those resistors? Thank you.

frank · Post by **frank** » Wed May 29, 2013 12:41 pm

Using pull-up or pull-down depends on the type of switch used, how it's wired, etc. But as I believe the '148 drives both high and low you will not need any resistors on S0, S1 and S2.