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Clock enquiry

Honored Contributor II

I am using an FPGA board with a CYCLONE (EP1C3T100C6). I want to locate a clock signal as output from the cyclone. I see pins such as 66, etc marked as CLK2, etc. Are these pins outputs or inputs? In general, I need to assign a Cyclone pin as a clock pin to a D flip flop. Help. 


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Honored Contributor II

The pin you refer to is a dedicated clock INPUT pin. So, don't expect to be able to drive a clock signal out of it. 


This pin would be ideal for sourcing a clock into the clock input of a D-type flip-flip - as you go on to describe. 


Finally, the clock signal you wish to drive out of the FPGA. Simplistically, you can drive a 'clock' (or any other) signal out of any of the 'IO' pins. This can be either; a clock of the same frequency you put into the device; a higher frequency clock - generated using the device's PLLs; or a lower speed clock using either the PLLs or logic (D-types). Refer to the document "using plls in cyclone devices (" - for details as to the clock in and out requirements for Cyclone PLLs. 



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