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Xilinx Constraints Guide

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HU_SET (HU Set)<br />

The HU_SET (HU Set) constraint:<br />

• Is an advanced mapping constraint.<br />

• Is defined by the design hierarchy.<br />

• Allows you to specify a set name.<br />

Chapter 4: <strong>Xilinx</strong> <strong>Constraints</strong><br />

Note It is possible to have only one H_SET within a given hierarchical element, but<br />

by specifying set names, you can specify several HU_SET sets.<br />

NGCBuild hierarchically qualifies the name of the HU_SET as it flattens the design and<br />

attaches the hierarchical names as prefixes.<br />

Differences Between HU_SET and H_SET<br />

HU_SET H_SET<br />

Has an explicit user-defined and hierarchically qualified<br />

name for the set<br />

Starts with the symbols that are assigned the HU_SET<br />

constraint<br />

Architecture Support<br />

Applicable Elements<br />

Has only an implicit hierarchically qualified name generated<br />

by the design-flattening program<br />

Starts with the instantiating macro one level above the<br />

symbols with the RLOC constraints<br />

For more information about set attributes, see Relative Location (RLOC).<br />

Applies to FPGA devices. Does not apply to CPLD devices.<br />

This constraint may be used with an FPGA device in one or more of the following design<br />

elements, or categories of design elements. Not all devices support all elements. To see<br />

which design elements can be used with which devices, see the Libraries <strong>Guide</strong>s. For<br />

more information, see the device data sheet.<br />

• Registers<br />

• FMAP<br />

• Macro Instance<br />

• ROM<br />

• RAMS, RAMD<br />

• MULT18X18S<br />

• RAMB4_Sm_Sn, RAMB4_Sn<br />

• RAMB16_Sm_Sn, RAMB16_Sn<br />

• RAMB16<br />

• DSP48<br />

Propagation Rules<br />

This constraint is a design element constraint. Any attachment to a net is illegal.<br />

Syntax Examples<br />

The following examples show how to use this constraint with particular tools or<br />

methods. If a tool or method is not listed, you cannot use this constraint with it.<br />

<strong>Constraints</strong> <strong>Guide</strong><br />

UG625 (v. 13.2) July 6, 2011 www.xilinx.com 131

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