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Altera_Forum
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12 years ago

Connection the Internal Oscillator to the PLL Input Clock in Cyclone III

Hello, I was wondering if it is possible to connect the internal oscillator to the reference clock in a Cyclone FPGA. It just wouldn't synthesise when I tried it earlier today. It gives the fol...
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Altera_Forum
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12 years ago

No, it's not possible to drive a PLL directly.

Also, note that the internal oscillator does not produced a clock with a stable, well known, frequency.

Even if you feed it through an external pin, the PLL will probably not work properly.