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AR# 22313

10.1 Constraint Syntax - What are legal values for IOBDELAY for Spartan-3E?

Description

The Constraint states that the IOBDELAY constraint can be used to set the IOB delay type for a Spartan-3E device. However, when I follow the given attribute and settings, the following warnings occur in the software:

"WARNING:NgdBuild:488 - Attribute value "IFD" is not an accepted value for attribute "IOBDELAY" on "IO_name"."

"WARNING:NgdBuild:488 - Attribute value "5" is not an accepted value for attribute "IOBDELAY" on "IO_name"."

"WARNING:NgdBuild:488 - Attribute value "IBUF" is not an accepted value for attribute "IOBDELAY" on "IO_name""

"WARNING:NgdBuild:488 - Attribute value "BOTH" is not an accepted value for attribute "IOBDELAY" on "IO_name"."

Then, the MAPPER fails with the following message:

"ERROR:Pack:657 - Invalid "IOBDELAY" property value of '5' found on symbol "IO_name". The only legal values for "IOBDELAY" are "NONE", "BOTH", "IBUF", and "IFD"."

What are the legal values for IOBDELAY for Spartan-3E?

Solution

The following attributes can be used to set the IOBDELAY element for Spartan-3E:

IBUF_DELAY_VALUE (accepted values are 0 -16)

IFD_DELAY_VALUE (accepted values are AUTO, 0 to 8)

For example, in your UCF:

NET "input_port_name" IBUF_DELAY_VALUE = 2;

NET "input_port_name" IFD_DELAY_VALUE =3 ;

For more information, refer to the Spartan-3E Libraries Guide in the software manual.

You can also refer to the Spartan-3E Complete Data Sheet (DS312), see Module 2: Functional Description:

http://www.xilinx.com/xlnx/xweb/xil_publications_index.jsp
Under FPGA Device Families, navigate to Spartan-3E -> Spartan-3E Complete Data Sheet (all four modules) -> Module 2: Functional Description.

AR# 22313
Date Created 09/04/2007
Last Updated 12/15/2012
Status Active
Type General Article