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How to update PLL frequency in TimeQuest

Altera_Forum
Honored Contributor II
1,186 Views

Hi. 

I have source clk 250 MHz and PLL that generates 130 MHz from it. When I changed output PLL frequency to 150 MHz, my design has been faster, but TimeQuest "Report Clocks" reported about old frequency, 130 MHz. How can I update frequency? 

And what should I also constrain for PLL? 

Thank you.
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Altera_Forum
Honored Contributor II
495 Views

OK, I've found the solution: 

1. Change PLL output frequency in Wizard. Remember High and Low parts of M, N, C counters. 

2. Open your SDC file and find PLL VCO and output clocks definitions (create_generated_clock). 

3. Edit VCO clock constraint: Fvco = Fin * M / N, so we should to edit "-multiply_by <M_value> -divide_by <N_value>", where each X_value = X_high + X_low, which we knew from step 1. 

4. Edit output clock constraint: Fout = Fvco / C, so we should to edit "-divide_by <C_value>". C_value = C_high + C_low, of course. 

Maybe exists another method?
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