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Clock enquiry

Altera_Forum
Honored Contributor II
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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. 

 

Andrew
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Altera_Forum
Honored Contributor II
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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 (http://www.altera.com/literature/hb/cyc/cyc_c51006.pdf)" - for details as to the clock in and out requirements for Cyclone PLLs. 

 

Regards, 

lex
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