Upgrade of 2008 R2 SP3 stops 2008 instance

Hello,

I have a server with both SQL 2008 and SQL 2008 R2 and am in the process to update the 2008 R2 version.

So my question is as follows:
If I upgrade 2008 R2 to the newest version does this interrupt connectivity to the 2008 instance? Or is the 2008 always available through out the process fo upgrading 2008 R2?

Regards

Paul