AR# 38651

MIG 3.6 Spartan-6 - DDR termination recommendation


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.


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):
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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AR# 38651
Date 03/04/2013
Status Active
Type General Article