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AR# 41310

MIG Spartan-6 MCB - How to use Self Refresh with the Spartan-6 Suspend Feature

Description

This section of the MIG Design Assistant focuses on the Self Refresh with Suspend Operation, as it applies to the MIG Spartan-6MCB designs.

Note: This Answer Record is a part of the Xilinx MIG Solution Center (Xilinx Answer 34243). The Xilinx MIG Solution Center is available to address all questions related to MIG. Whether you are starting a new design with MIG or troubleshooting a problem, use the MIG Solution Center to guide you to the right information.

Solution

The Spartan-6 family offers the suspend mode, an advanced static power-management feature, which reduces FPGA power consumption while retaining the FPGA configuration data and maintaining the design. The Spartan-6 device can quickly enter and exit suspend mode as required in an application.Using the Spartan-6 FPGA suspend mode with the DRAM self refresh feature allows you to realize significant power savings during longer periods with no memory access. For additional information on the suspend mode, see the Spartan-6 FPGA Power Management User Guide(UG394).

There are two recommended methodsfor using the Suspend Mode capabilities of Spartan-6 devices with designs containing an MCB-based interface:"Suspend Mode with DRAM Data Retention" and"Suspend Mode without DRAM Data Retention".The following section descibes the "Suspend Mode with DRAM Data Retention" method. Additional details on this method as well as the"Suspend Mode without DRAM Data Retention" method can be found the in the "Suspend" section of "Chapter 4: MCB Operation" in the the Spartan-6 FPGA Memory Controller User Guide(UG388).

Suspend Mode with DRAM Data Retention

During suspend mode,the Spartan-6 retains FPGA configuration data and the state of the FPGA application.This is one of the key properties that enables this method.Several other conditions have to be met for the"Suspend Mode with DRAM Data Retention" method to work properly.

  1. The SUSPEND_SYNC primitive must be used in combination with the Self Refresh interface of the MCB. The SUSPEND_SYNC primitive is used to ensure that the MCB puts the DRAM device into self-refresh modeto retain its state prior to putting the FPGA into suspend mode.
  2. The proper I/O behavior during the suspend mode has to be defined on the memory interface.That means that for the CKE signal for DDR/DDR2/DDR3 memories and for thenRESET signal forDDR3 interfaces the SUSPEND attribute must be set to DRIVE_LAST_VALUE in the UCF to avoid havingtheexternal pull-down resistor on those signals pull them low during suspend mode.
  3. The suspend feature has to be enabled with the Glitch Filtering option.The recommended method is to use the CONFIG statement in the UCF.Config ENABLE_SUSPEND = "FILTERED";

Suspend mode with DRAM data retention is supported in MIG 3.8 and newer designs.

Linked Answer Records

Associated Answer Records

Answer Number Answer Title Version Found Version Resolved
40737 MIG Spartan-6 MCB - Self-Refresh as defined by JEDEC Specification N/A N/A
AR# 41310
Date Created 08/22/2011
Last Updated 12/15/2012
Status Active
Type General Article
Devices
  • Spartan-6 LX
  • Spartan-6Q
  • Spartan-6 LXT
IP
  • MIG