AR# 21820: 7.1i EDK - Base System Builder (BSB) is generating incorrect DCM settings for Virtex-4
7.1i EDK - Base System Builder (BSB) is generating incorrect DCM settings for Virtex-4
Keywords: DFS, ML-403, ML403, PPC
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
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