Forum Discussion

Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
12 years ago

Implementing User-Defined "Wait For" time

Disclaimer: I'm a noob I'm trying to implement an entity which takes as an input a 16-bit binary number called bounceWidth( in std_ulogic_vector(15 downto 0)) which will represent the time in ...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
12 years ago

--- Quote Start ---

So I'm looking at an example from a website called VHDL Guru and they have an example of a 4-bit Johnson counter, but I'm not sure of is how many bits should be sufficient for a counter to gauge time duration? I was told that the range of time I may want to consider would be 0.1 to 10ms.

--- Quote End ---

I'd never heard of a Johnston counter but a quick google shows it's just a massive shift register.

If you've a 10MHz clock you'll need ~ 100,000 bits in your counter for 10ms.

Why not just use a 17 bit binary counter to trigger transitions?

Nial