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AR# 25104

MIG v2.2 - Why were the hand-modifications to the "rtl" and "sim" files listed in the Spartan-3A Starter Kit Board files "Readme.txt" required?


The "Readme.txt" file included with the Spartan-3A board files generated by MIG 2.3 includes the following comments:

"There were several hand-modifications to the 'rtl' and 'simulation' files required for the core to be targeted on the Spartan-3A Starter Kit."

Seven changes are then listed. Two of the changes noted are the following:

5. Added one more file ram8d_1 for strobe 2 and modified the WCLK for proper routing in ram8d_0 and ram8d_1.

6. Changed the instantiation name for strobe 2 from ram8d_0 to ram8d_1 in data_read module.

Why were these two changes required?

NOTE: This information has been moved to the README file for the Spartan-3A Starter Kit. Please refer to the README file for full details.


The board files do not follow a few of the RTL rules required for designs generated by the MIG tool. For this reason, the hand-modifications noted were required. These modifications are included in the Spartan-3A Starter Kit board files.

Following are the rules that must be followed with the board files:

  1. When DQ signals are allocated, the top pad should always have the even-numbered DQ and the bottom pad should always have the odd-numbered DQ.
    • This rule is violated so that the DQ routes from PAD to the slices will take longer delays. For example, DQ7 is connected to the top pad and DQ0 is connected to the bottom pad.
  2. No two even DQ signals, nor two odd DQ signals, should go to the same I/O tile.
    • This is violated in some cases on the Spartan-3A Starter Kit Board. For example, DQ15 and DQ9 are connected to the same I/O tile, and DQ14 and DQ10 are connected to the same I/O tile. If you want to have two odd pins or two even pins in a tile, it is required to change the "rtl." The delayed dqs connection in the RAM8D module must be changed accordingly.
  3. The top pad DQ should use the first column, and the bottom pad DQ should use the second column.
    • This is also violated.

When these rules are violated, the following changes are made to the default Spartan-3A DDR2 MIG output:

  1. Delete the RAM8D_0 module from the tool output.
  2. Copy the RAM8D_0 and RAM8D_1 modules for the board files and paste them into the "rtl" folder.
  3. Instantiate these two files in the data_read module: RAM8D_0 is for DQS0, and RAM8D_1 is for DQS1.
AR# 25104
Date 12/15/2012
Status Active
Type General Article
  • Spartan-3A
  • MIG
Boards & Kits
  • Spartan-3A Starter Kit
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