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Honored Contributor
Honored ContributorCyclone II: PLL
From the device datasheet Cyclone II has 4 PLL, and I need to generate four 250MHz clocks with 0 degree, 90 degree, 180 degree and 270 degree phase shift. The input clock is 50MHz. But the altpll fun...
Altera_ForumHonored Contributor
Honored Contributor --- Quote Start --- You can do a NOT gate or rising/falling edge. There is an inversion as the clock goes into the LAB that has negligible delay. --- Quote End --- Being (a bit) pedantic: as shown on page 2-9 (http://www.altera.com/literature/hb/cyc2/cyc2_cii51002.pdf) there is a mux that selects between the 'true' and the 'inverted' global(s) to feed the LAB. If there is any difference in the delay I expect TimeQuest will take that into account. --- Quote Start --- Strictly NO !, you can't "shift 180°" with NOT gate because gates introduce a delay, so 180° is NOT guaranteed by this way. --- Quote End --- 'Definitely YES' I'd say ...
