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AR# 21820

7.1i EDK - Base System Builder (BSB) is generating incorrect DCM settings for Virtex-4

Description

Keywords: DFS, ML-403, ML403, PPC

Urgency: Standard

General Description:
When I target an ML-403 board, EDK sets the DCM C_DFS_FREQUENCY_MODE parameter incorrectly. According to the Virtex-4 DC and Switching Characteristics Data Sheet, whenever Clkfx is above a certain frequency range, the DFS_FREQUENCY_MODE needs to be set to High. Refer to the Virtex-4 DC and Switching Characteristics Data Sheet to find the tolerances for the specific Virtex-4 speedgrade when the DCM is in "Low Frequency Mode" and "High Frequency Mode."

For example, the ML-403 development board comes with a -10 speedgrade part:
Clkfx Low Frequency range 32 MHz - 210 MHz
Clkfx High Frequency range 210 MHz - 300 MHz

Solution

Normally, the C_DFS_FREQUENCY_MODE parameter is not added to the project.

To work around this issue:
1. Select the Add / Edit Cores dialog
2. Select the Parameters tab
3. Change the core to the dcm_x
4. Add the C_DFS_FREQUENCY_MODE parameter
5. Change the parameter from Low to High
AR# 21820
Date Created 07/27/2005
Last Updated 04/16/2007
Status Archive
Type General Article