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AR# 30788

MIG v2.2, QDRII Virtex-5 - DCI_CONFIG setting is incorrect in UCF when Data Read banks are in two different columns for x18 36-bit designs


When generating an x18 36-bit QDRII design for Virtex-5, if the two Data Read banks are selected in two different columns, the generated UCF file contains the wrong DCI Cascade settings.

This causes the following error during BitGen:

ERROR:Bitgen:282 - Bank 18 cannot be specified as a DCI slave because it already has a different DCI setting.

Manual modification is required.

Starting with MIG 2.3, the Memory Interface Solutions User Guide (UG086) includes the appropriate steps to follow regarding this issue.


To accommodate a QDRII Virtex-5 36-bit data width design with x18 parts, two banks are required - 18-bits in each bank.

There are two options for bank selections, selecting banks in the same column or two different columns.

By default, MIG enables the option "DCI Cascade" in either case.

If you select the two Read Data banks in the same column, one of the selected read banks (or any other bank in the same column) can be selected as the Master Bank.

Either option is viable and causes no issues.

If you select the Read Data banks in two different columns, a Master Bank must be selected in each column.

Because MIG has enabled the "DCI Cascade" option, if you select the Read Data bank as the Master Bank, then the Master Bank and Slave Bank would be same.

The syntax for Master bank is as follows:

DCI_CONFIG = "Master bank number Slave bank number;"

In the above case, since the Master bank and Slave bank are the same, the syntax in the MIG output UCF file is as follows:

DCI_CONFIG = "18 18"; (assuming that bank 18 is selected for Data Read)

Selecting the Master and Slave banks in the same bank is not a valid configuration.

This causes BitGen to fail with the following error:

ERROR:Bitgen:282 - Bank 18 cannot be specified as a DCI slave because it already has a different DCI setting.

You can use one of the following methods to work around this issue:

  • When only one Read Data bank is selected in any column, "DCI Cascading" is not required.
    MIG cannot determine what your banks selections will be; consequently, the "DCI Cascade" option is enabled by default.
    If you select two different banks in different columns, you can disable the "DCI Cascade" option.

  • You can select a different bank than the Read data bank but in the same column as the "Master bank" .
    This is not a recommended solution, because it wastes pins.
AR# 30788
Date Created 04/17/2008
Last Updated 07/30/2014
Status Active
Type General Article
  • Virtex-5 FXT
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