Sign in to follow this  
Followers 0
FantomXR

Why does the HC165 even work?

4 posts in this topic

Hey people,

I try to understand how the DIN is even working in the STM32F4-Core. 
PB14 is not going through the HCT541 buffer. It goes directly into the IC. If I understood it correctly the purpose of the HCT541 is to do a level-amplification. It takes the level from the STMs outputs (which is 3.3V - 0.4V for HIGH for CMOS or 2.4V or TTL) and amplifies them. As the HC165 and HC595 are powered from +5V they need 3.15V to see a HIGH-signal. As the HCT541 delivers 4.5V for HIGH the HC595 does of perfectly work.

But why do the HC165 even work? As I said it doesn't get an amplification. So in theory the HC165 sees 2.9V for HIGH but that's not enough so it should stay LOW and doesn't work. But it does...

Can someone explain this behavior?

Thanks,
Chris

Share this post


Link to post
Share on other sites
9 minutes ago, FantomXR said:

As I said it doesn't get an amplification

??
QH pin which is connected to the STM on SI, is an output! It sends 5V cmos level to the STM, the inputs pin of the STM are '5V tolerant' then you don't need level shifting down in this way(165 to STM).
 

Edited by Antichambre

Share this post


Link to post
Share on other sites

Oh dear... thanks for clearing my mind! ;-)

BTW: Do you watch this forum all day? ;-) 

Share this post


Link to post
Share on other sites
20 minutes ago, FantomXR said:

BTW: Do you watch this forum all day? ;-) 

lol
Yeah I've got some default pages opened when my computer is switched on, all my email boxes, messenger and midibox forum!
My computer is always switched on when I'm home. And I work 80% of the time at home so. ;)

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0