R
Chapter 5: Constraining the Core
Timing Ignore Constraints
If Source core static configuration signals are driven statically from a register, apply the timing ignore attributes (TIG) to the static configuration signals to create proper timing ignore paths. If these are driven statically from a wrapper file, then the TIG is not needed.
In the example UCF, these constraints are commented out. Uncomment these constraints in your design.
•NET "SrcAFThresAssert(*)" TIG;
•NET "SrcAFThresNegate(*)" TIG;
•NET "DataMaxT(*)”;
•NET "AlphaData(*)”;
•NET "SrcBurstLen(*)”;
•NET "NumDip2Errors(*)”;
•NET "NumDip2Matches(*)”;
User Constraints
In certain cases, you may need to add additional constraints to cover other logic implemented in your design. While the UCF file provided with the core is designed to completely constrain the Xilinx
Constraints Migration
The example UCF file provided with the core must be modified to migrate the core to a different area or target device.
The examples in this section indicate the changes necessary to migrate the Sink and Source cores to
New Target Region or Device Package
When selecting a new target region or device package, first verify that the new region has enough resources required for the generated core. Resources that need to be taken into considerations are:
•Block RAMs
•I/O Pins (in targeted I/O banks)
•Logic cells
•Clocking resources: DCM, regional and global buffers
Below are some typical region selections within a device.
•Source Core: One clock region on the same side of the device, east or west.
•Sink Core (static): One clock region on the same side of the device.
The east side is the side of the device with even numbered I/O banks: 6, 8, 10, and so on.
The west side is the side of the device with odd numbered I/O banks: 5, 7, 9, and so on.
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| UG181 June 27, 2008 |