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Altera_Forum
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15 years ago

Cyclone ALTPLL questions

Hello! I have two simple questions regarding the use of PLL in a Cyclone I EP1C3 device. 1) I would like to have a 20 MHz input clock (inclk0) and two output clocks, one with the same freq...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
15 years ago

Cyclone PLL won't accept 5 MHz input clock. If you use an external PLL, both clocks would be "unrelated" (have undefined phase relation) as well. A clock divider is definitely the way to go, if both clocks are intended to be used in the same design entity. If both clocks are driving completely separated entities, a ripple clock doesn't cáuse problems in timing closure.