Resolve all 4 inter-clock timing violations found in Vivado synthesis
attempt #11 (WNS was -2.552 ns). Changes:
- Add reset synchronizer for clk_120m_dac domain (2-FF chain)
- Add Gray-code CDC for chirp_counter (6-bit, 120MHz->100MHz)
- Add single-bit CDC for new_chirp_frame (3-stage, 120MHz->100MHz)
- Add 2-stage input synchronizers for valid signals in USB module
(clk_100m->ft601_clk_in) with data capture on rising edge
- Fix ft601_clk_out multi-driven net (removed duplicate assignment)
- Update XDC: set_max_delay -datapath_only for CDC, false_path for reset
Result: Vivado attempt #12 passes with 0 errors, 0 timing violations,
and 'All user specified timing constraints are met.' (WNS +0.983 ns)
Jason
ffed7c1623