Xilinx Answer #5675 : Virtex: Virtex doesn't have IFDs and OFDs

Answers Database

Virtex: Virtex doesn't have IFDs and OFDs

Record #5675
Product Family: Hardware

Product Line: Virtex

Product Part: Virtex General Hardware

Problem Title:
Virtex: Virtex doesn't have IFDs and OFDs

Problem Description:
Urgency: Standard

Problem descriptions: Virtex devices no longer have IFD and OFD components.

Solution 1:

Virtex family no longer uses IFDs and OFDs to represent IOB FFs. Both UNISIMS
and SIMPRIMS libraries don't have simulation models for IFDs and OFDs.
Virtex IO FFs are essentially the same as FDCEs with clock enable and clear. There are two ways to utilize IOB FFs in Virtex:

1. Use IOB=TRUE property in either the UCF file or the synthesis tools. UCF syntax: INST name IOB=TRUE;

2. Use -pr {i | o | b} option in MAP, where i stands for input FF, o stands for output FF, and b stands for both input and output.

Solution 2:

The schematic libraries still have IFDs and OFDs as valid components. The purpose of having the schematic version is for design migration capabilities. The IFD is made of an IBUF cell and a FD cell. The OFD is made of a FD cell and an OBUF cell.

End of Record #5675 - Last Modified: 05/03/99 15:17

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