Xilinx Synthesis Technology User Guide

XST User Guide
You may specify the same attribute in the XCF file with the following
lines:
MODEL ENTNAME
NET s PWR_MODE=LOW;
NET s KEEP;
END;
The following statement is written to the NGC file by XST:
NET s PWR_MODE=LOW;
NET s KEEP;
If the attribute applies to an instance (for example, IOB, DRIVE,
IOSTANDARD) and if the instance is not available (not instantiated)
in the HDL source, then the HDL attribute can be applied to the
signal on which XST will infer the instance.
Third Party Constraints
This section describes constraints of third-party synthesis vendors
that are supported by XST. For each of the constraints, Table 5-5 gives
the XST equivalent and indicates when automatic conversion is
available. For information on what these constraints actually do,
please refer to the corresponding vendor documentation. Note that
“NA” stands for “Not Available”.
Table 5-5 Third Party Constraints
Name Vendor XST Equivalent
Available
For
black_box Synplicity box_type VHDL/
Verilog
black_box_pad_pin Synplicity NA NA
black_box_tri_pins Synplicity NA NA
cell_list Synopsys NA NA
clock_list Synopsys NA NA
Directives for inferring FF and
latches
Synopsys NA NA
Enum Synopsys NA NA
5-50 Xilinx Development System