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Altera_Forum's avatar
Altera_Forum
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18 years ago

Multicycle period & Multicycle hold

Anybody tell me what is the relationship between Multicycle period constraint/multicycyle hold constraint and wait time/pipelined transfer read latency?

I myself think:

Multicycle hold constraint =wait time;

Multicycle period constraint - Multicycle hold constraint -1 = pipelined transfer read latency;

Maybe I don't express my question clearly enough, but I hope for response anyway,you can just tell me that you don't understand my question, then I will try to correct my question.

Thanks...

My question comes from the post I sent before, pls see the following link for detailed info:

http://www.alteraforum.com/forum/showthread.php?p=6405#post6405 (http://www.alteraforum.com/forum/showthread.php?p=6405#post6405)

3 Replies

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

    I assume the source and destination clock is the same? The multicycles are based on that period. For example, if the clock period is 10ns, then the default setup requirement is 10ns and the default hold requirement is 0ns. Now, if your opening the window to say you have multiple clock periods to transfer the data, then most likely you will do a multicycle -setup value of N and a multicycle hold value of N-1. For example, if do:

    set_multicycle_path -setup 2 -from A -to B

    set_multicycle_path -hold 1 -from A -to B

    then you will have a setup requirement of 20ns and a hold requirement of 0ns. So your window is 20ns, and is twice as big to pass the data through. If you do:

    set_multicycle_path -setup 3 -from A -to B

    set_multicycle_path -hold 2 -from A -to B

    Then your setup requirement is 30ns and your hold is 0ns, for a 30ns window to pass the data through. I will try to add a presentation I worked on that goes through this soon.
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    18 years ago

    Hi, I understand what you mean clearly.

    but you seems to not answer my question directly. :)

    I need to comfirm the following equations:

    Multicycle hold constraint =wait time;

    Multicycle period constraint - Multicycle hold constraint -1 = pipelined transfer read latency;

    Are they right?

    Thanks for your response.
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    18 years ago

    I see, and correct, I did not answer your question. I don't deal with this much so don't have any read answers. Hopefully someone else will respond soon. (If you don't get anything, you might want to try niosforum.com)