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Xilinx Constraints Guide

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

MCB Performance (MCB_PERFORMANCE)<br />

Note This constraint applies to Spartan®-6 devices only.<br />

Spartan-6 devices have a Memory Controller Block (MCB) which can support two<br />

different performance targets depending on voltage settings and conditions on the<br />

VCCINT power supply. The performance targets are listed in the device data sheet. To<br />

specify the desired MCB performance level in the ISE® Design Suite tools, use the MCB<br />

Performance (MCB_PERFORMANCE) configuration constraint in the User <strong>Constraints</strong><br />

File (UCF) supplied to the tools upon implementation.<br />

MCB_PERFORMANCE is supported in the User <strong>Constraints</strong> File (UCF) only.<br />

The syntax is as follows:<br />

CONFIG MCB_PERFORMANCE=[STANDARD|EXTENDED];<br />

MCB_PERFORMANCE can be specified as follows:<br />

• None<br />

If MCB_PERFORMANCE is not specified, the default is STANDARD.<br />

• STANDARD<br />

To target the MCB to normal performance and the full voltage range on VCCINT as<br />

shown in the device data sheet, specify STANDARD in the UCF.<br />

CONFIG MCB_PERFORMANCE= STANDARD;<br />

• EXTENDED<br />

To target the MCB to a faster performance, specify EXTENDED in the UCF.<br />

CONFIG MCB_PERFORMANCE=EXTENDED;<br />

There are explicit voltage requirements when using EXTENDED. For more<br />

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

Note VCCINT voltage settings in the UCF and timing tools, and as reported by the<br />

ISE Design Suite tools, are independent of this setting. They may report a different<br />

voltage for analysis than required by the MCB_PERFORMANCE setting. Voltage<br />

requirements of this rail must be set properly based on both this attribute and the<br />

Voltage settings for timing analysis.<br />

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

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

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