Xilinx Constraints Guide

Chapter 4: Xilinx Constraints
You can assign soft macros and flip-flops to a single slice location, a list of slice locations,
or a rectangular block of slice locations.
Slice locations can be a fixed location or a range of locations. Use the following syntax
to denote fixed locations.
SLICE_XmY n
where
Slices Prohibited
m and n are the X and Y coordinate values, respectively
They must be less than or equal to the number of slices in the target device. Use the
following syntax to denote a range of locations from the highest to the lowest.
SLICE_X mYn:SLICE_XmY n
Format of Slice Constraints
The following examples illustrate the format of slice constraints: LOC= and the slice
location. If the target symbol represents a soft macro, the LOC constraint is applied to all
appropriate symbols (flip-flops, maps) contained in that macro. If the indicated logic
does not fit into the specified blocks, an error is generated.
Slice Constraints Example One
The following UCF statement places logic in the designated slice.
INST “instance_name” LOC=SLICE_X133Y10;
Slice Constraints Example Two
The following UCF statement places logic within the first column of slices. The asterisk
(*) is a wildcard character
INST “instance_name” LOC=SLICE_X0Y*;
Slice Constraints Example Three
The following UCF statement places logic in any of the three designated slices. There is
no significance to the order of the LOC statements.
INST “ instance_name” LOC=SLICE_X0Y3, SLICE_X67Y120, SLICE_X3Y0;
Slice Constraints Example Four
The following UCF statement places logic within the rectangular block defined by the
first specified slice in the lower left corner and the second specified slice towards the
upper right corner.
INST “ instance_name" LOC=SLICE_X3Y22:SLICE_X10Y55;
You can prohibit PAR from using a specific slice, a range of slices, or a row or column
of slices. Such prohibit constraints can be assigned only through the User Constraints
File (UCF). Slices are prohibited by specifying a Prohibit (PROHIBIT) constraint at the
design level, as shown in the following examples.
Slices Prohibited Example One
Do not place any logic in the SLICE_X0Y0. SLICE_X0Y0 is at the lower left corner of
the device.
Schematic None
UCF CONFIG PROHIBIT=SLICE_X0Y0;
Constraints Guide
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