Asynchronous clock switching circuits vs. BUFGMUX

[Jay]

Hi Peter,

I've used your Asynchronous clock switching circuits(Six Easy Pieces) in my
design. It works really good.

What I'm wondering is whether there's the same circuits in the BUFGMUX. Any
difference?

 

[Peter Alfke]

Unfortunately, there is a difference. The BUFGMUX has a set-up time
requirement for S, so it is not really asynchronous.
Both types of circuit have a common flaw: They do not work properly with
a clock of zero frequency...
For that you have to use the Enable option.
This is all being fixed in the next generation.

Peter Alfke
================
Jay wrote:

Hi Peter,

I've used your Asynchronous clock switching circuits(Six Easy Pieces) in my
design. It works really good.

What I'm wondering is whether there's the same circuits in the BUFGMUX. Any
difference?