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AR# 15619

5.1i SP1 BitGen, Virtex-II Pro - The "DCIUpdateMode" option is available (replaces the "FreezeDCI" option)


General Description:

In 5.1i Service Pack 1, a new BitGen option for Virtex-II Pro called "DCIUpdateMode" replaces the "FreezeDCI" option. What is the difference between the "FreezeDCI" and "DCIUpdateMode" options? When do I use which option?


This option is included in the latest 5.1i Service Pack, available at:

The first service pack containing the fix is 5.1i Service Pack 1.

The syntax for "DCIUpdateMode" is as follows:

-g DCIUpdateMode:<mode>


- You should still use the "FreezeDCI" option for Virtex-II and certain early release of Virtex-II Pro devices (i.e., 2VP4 and 2VP7).

Note that setting FreezeDCI:Yes will result in a slightly larger bitstream.

- For 2VP4 and 2VP7, the device supporting DCIUpdateMode can be identified with 3-letter code and JTAG ID as described in (Xilinx Answer 17244).

- All other Virtex-II Pro devices support the "DCIUpdateMode" BitGen option. For more information on the "FreezeDCI" option, see (Xilinx Answer 13012).

- For all Virtex-II Pro devices supporting DCIUpdateMode, FreezeDCI must be set to "NO".

Mode Description

Mode can be Continuous, AsRequired, or Quiet as described below:

Continuous: Impedance adjustments are made continuously (exhibits the same update behavior as Virtex-II and early Virtex-II Pro silicon (V2P4, V2P7).

AsRequired: Impedance adjustments are made only when needed (default).

Quiet: After an initial impedance match is achieved, no further impedance adjustments occur (similar to the "-g FreezeDCI:Yes" option).

The DCI circuitry has an internally generated clock. This clock can cause an amplitude modulated (AM) signal with some I/O standards, most notably with SSTL2_I_DCI, SSTL2_II_DCI, SSTL3_I_DCI, SSTL3_II_DCI, LVDS_25_DCI, and LVDSEXT_25_DCI. This issue is described further in (Xilinx Answer 13012).

To resolve these problems, the DCI clock can be turned Off after configuration.

The two settings are related as follows:

DCIUpdateMode:Continuous..................................FreezeDCI:No (DEFAULT)

DCIUpdateMode:AsRequired (DEFAULT)..............No equivalent


AR# 15619
Date Created 09/03/2007
Last Updated 12/15/2012
Status Active
Type General Article