10-14-2014 06:34 AM
Im using dcm block for clock divider in spartan3,but im getting the below error at mapping stage??
CLKFB pin of DCM symbol "dcm/DCM_inst" is connected to GND. In
this configuration, only the CLKFX or CLKFX180 pin can be used. Otherwise,
correct clock path delay cannot be determined.
Thanks in advance!!
10-14-2014 06:51 AM
CLKFB -- Clock feedback input to DCM. The feedback input is required unless the Digital Frequency Synthesis outputs, CLKFX or CLKFX180, are used stand-alone. The source of the CLKFB input must be the CLK0 or CLK2X output from the DCM and the CLK_FEEDBACK must be set to 1X or 2X accordingly. The feedback point ideally includes the delay added by the clock distribution network, either internally or externally.
So CLKFB pin must not be connected i.e., should not be grounded.
From the message, it seems like you have not connected CLKFB pin or connected to GND.
10-16-2014 01:32 AM