gpio frequency

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originally posted by wave_runner@Feb 27 2007, 09:23 PM

what's the fastest frequency we can sample through a gpio header on the de2 board with a cyclone ii fpga?

the clock on the board is 50 mhz and when we put it through the sopc builder and then output it using nios ii (through a gpio header) using c and measuring the frequency through an o-scope, our output is consistently 333 hz. is this normal? and if not, shouldn't our frequency be 50 mhz?

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What exactly do you want to do?

If you want to have a 50MHz or a faster clock output on one of the gpios you can use a pll. Implement it in SOPC Builder (Others -> PLL) and lunch the MegaWizard, input frequency would be 50 MHz and output c2 can also be used as external output. Use output c2, set it to a frequency where it says "Able to implement the requested pll" and finish. At the System Contents tab of the SOPC Builder on the upper right corner you see the list of clocks. Check the name of c2 of the pll and on the Board Settings tab connect this clock under the global_signals with your gpio pin.

If you want to change the output of a gpio controlled by a C program on the Nios II with a certain frequency you could use an interrupt.

Hope this helped.