AR# 5304: Virtex - What is an IBUFG, and how do I use it?
Virtex - What is an IBUFG, and how do I use it?
Keywords: IBUFG, clock, buffer, input
General Description: What is the IBUFG primitive in Virtex? What is its purpose?
The IBUFG is a dedicated clock input pin for a DLL or associated BUFG. There are four IBUFG pins, one for each DLL/BUFG.
These pins are input-only and can use one of the many input voltage standards available. Banking rules must be followed. (The associated bank number is available in the Virtex data sheets for a given device/package combination.)
The IBUFG contains a dedicated route to its associated DLL. This ensures increased accuracy and the smallest delay in use of the DLL. Similarly, the IBUFG can be routed to user logic and does not need to be routed to a DLL.
Please note that if an IBUFG is not used as an input to the DLL, additional delay is being introduced.
Please refer to the SW Manuals -> 'Libraries Guide' -> Design Elements for more information on how to instantiate IBUFG.