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RE: Control line pull-ups on mixed 3v/5v system



Title: Control line pull-ups on mixed 3v/5v system
Wayne
 
The pull up-values specified are different for 3.3volt and 5 volt signaling.
 
We used PI5C3257 to switch between 1K and 2.7K. We also used a VIO detect circuit to do the switch automatically.
 
Regards
Joe
 
-----Original Message-----
From: Wayne Eckertson [mailto:WayneEckertson@VersaLogic.com]
Sent: Monday, July 22, 2002 12:25 PM
To: 'pci-sig@znyx.com'
Subject: Control line pull-ups on mixed 3v/5v system

I am designing a system which will support either 3V or 5V PCI adapter cards (not at the same time).  On-board devices are 3.3V, 5V tolerant.  Which rail should the control lines be pulled to?  More simply, will a 3V only device have problems if the control lines are pulled to the 5V rail and vise-versa?


Wayne Eckertson
waynee@versalogic.com
R+D Engineer
VersaLogic Corp