AR# 38651

MIG 3.6 Spartan-6 - DDR termination recommendation

Description

DDR memories do not support on-die termination (ODT), therefore, external memory terminations have to be provided. Spartan-6 FPGAs provide optional calibrated or uncalibrated input termination.MIG allows you to select calibrated or uncalibrated termination on the Spartan-6 FPGA, but selecting these options results in a non-working design.Therefore, you should only select "External Input Termination" in the "FPGA Options" page in MIG.

Solution

There is no on-die termination supportfor DDR memories, therefore, external terminations have to be provided.Theexternal memory terminations should be placed after the associated memory component in a fly-by fashion.
For more information onPCB layout considerations seethe"Spartan-6 FPGA Memory Controller" User Guide (UG388):
http://www.xilinx.com/support/documentation/user_guides/ug388.pdf
Because the external termination is required for DDR, you should not select any internal termination in the Spartan-6FPGA.For DDR interfaces,you should select"External Input Termination" in the "FPGA Options" page in MIG 3.6.Upcoming versions of MIG will have the option to select calibrated or uncalibrated input termination for DDR interfaces disabled.

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Linked Answer Records

Associated Answer Records

Answer Number	Answer Title	Version Found	Version Resolved
40778	MIG Spartan-6 MCB - Termination and I/O Standard Guidelines	N/A	N/A
39128	MIG Virtex-6 and Spartan-6 v3.7 - Release Notes and Known Issues for ISE Design Suite 13.1	N/A	N/A
38951	MIG v3.61 - Release Notes and Known Issues for ISE Design Suite 12.4-14.2	N/A	N/A

AR# 38651
Date	03/04/2013
Status	Active
Type	General Article
Devices	Spartan-6 LX Spartan-6 LXT
IP	MIG

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