Hi All,
It is obviously my fault, and the correct answer is probably "RTFM" (1), but I've just lost significant amount of time, because TimeQuest treats clocks as related by default. The design which worked perfectly compiled with standard Timing Analyzer, got crazy after switching to TQ. I discovered the problem when I got strange warnings like:
"Warning: 26 (of 12252) connections in the design require a large routing delay to achieve hold requirements. Please check the circuit's timing constraints and clocking methodology, especially multicycles and gated clocks."
The TQ considers all clocks as related unless specified otherwise. Is it reasonable to consider two clocks with different frequences (e.g. 10.3213 MHz and 13.43345 MHz - just the random values) as related? In this case there must be ALWAYS ts and th violations. Shouldn't the TQ loudly complain about not specified relationships between the clocks instead of assuming by default that all clocks are related?
-- TIA & Regards, Wojtek.
(1) qts_qii53019.pdf
Page 7-1: All clocks are related by default. (Refer to "Related and Unrelated Clocks" on page 7-=AD13.) Page 7-13: Related and Unrelated Clocks In the Quartus II TimeQuest Timing Analyzer, all clocks are related by default, and you must add assignments to indicate unrelated clocks. However, in the Quartus II Classic Timing Analyzer, all base clocks are unrelated by default. All derived clocks of a base clock are related to each other, but are unrelated to other base clocks and their derived clocks.
Then on 7-14 it is explained how to set clocks to unrelated with set_clock_groups -exclusive -group {clock_a} -group {clock_b}