A strange error

Altera_Forum · ‎01-20-2012

Hi !

When I exactly follow the 《Nios II Hardware Development Tutorial》 to the end of adding contants ( page 1-23 ) , a strange error say " Error: System.cpu: Nios II debug module requires a clock frequency of at least 20 MHz " .

But my clock setting is just set to 20 MHz .

What's the problem ?

Altera_Forum · ‎01-20-2012

Try 50 MHz - usually safe

Altera_Forum · ‎01-20-2012

I set to 20 MHz because my oscillator on development board is 20 MHz .

Seems I need to use pll to rise the frequency ?

But the tutorial say "The

frequency you specify for clk_0 must match the oscillator that drives the FPGA."

Altera_Forum · ‎01-20-2012

That's an error, it should say it must match the clock signal driving the cpu.

We run the Nios through a PLL all the time. So bumping to 40 , 60, 80, or 100 MHz should be no problem from your 20 MHz source.

Just for grins I would just switch the setting to 20.1 MHz and see if it builds. I never hit that before, but it sounds like someone in the software land should have had made it the limit >= instead of just >.

Pete