AR# 34137

描述

MIG v3.3 allows the following drive strengths to be selected for the Spartan-6 FPGA LPDDR design:

• Full-Strength
• Half-Strength
• Quarter Strength
• One-eighth Strength

There are two issues with these settings:

1. While One-eighth is an optional setting defined by JEDEC, Micron does not support this option. The next release of MIG will remove the One-eighth setting.
2. The corresponding Output Drive Strength parameter (Cx_MEM_MDDR_ODS) does not get set appropriately. This parameter is always set to "FULL" regardless of the selection in the MIG tool. This Answer Record details the steps to work around this issue.

解决方案

This issue is Fixed in ISE Version 12.1.

To work around this issue, you need to manually change the Cx_MEM_MDDR_ODS parameter to the appropriate value.

Step 1

Open the top-level module ("example_design/rtl/example.top.v/vhd" or the "user_design/rtl/<comp_name>.v/vhd") and locate the Cx_MEM_MDDR_ODS parameters.
There is a unique parameter for each controller in the MIG design.

• localparam C1_MEM_MDDR_ODS         = "FULL"; 
• localparam C3_MEM_MDDR_ODS         = "FULL"; 

Step 2

Change the "FULL" setting to the desired output drive strength.
The supported settings are:

• "FULL"
• "HALF"
• "QUARTER"