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Altera_Forum's avatar
Altera_Forum
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13 years ago

clock distribution in quartus

Hello all,

are there any tutorials/help documents concerning how the clock signals

should distributed in quartus?

the problem i have is that when my quartus/nios project reaches a certain

size the pll can't generate a 80MHz clock anymore.

the project has one big nios and several mmp blocks, all running with the same 80MHhz clock.

should i us one pll which generates one clock signal for all (nios+mmps) or one pll generating four 80MHz signals. when should the global primitive be used?

thanks in advance!

2 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    13 years ago

    Quartus automatically uses the global clock network, and you can use a single clock in all your design, it shouldn't depend on the project size.

    What do you mean by "can't generate"? What error message do you get?
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    13 years ago

    thanx for your reply, my PLL does not lock anymore, but you are right that the project size is not the problem. Some additional MMPs caused the problem (setup and hold violations).