When I constrain the input clock of DCM and use its output clocks to drive the design, I notice different results between the data sheet section and the timing constraints report. Why does this occur?
This is a limitation of the data sheet report; it does not take into account "multiplied by and duty cycle correction" which is derived for DCM's output. Below is an example:
Timing constraint: PERIOD analysis for net "dcm_clk200/clkfx_dcm" derived from
net "buf_clk200" PERIOD = 4.95 ns HIGH 50%
INPUT_JITTER 0.15 ns;
multiplied by 2.00 and duty cycle corrected to 9.900 nS HIGH 4.950 nS
If the timing constraint does not have this content, the data sheet report and timing constraint report will have the same PERIOD number.
This issue will be fixed in a future release.