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What does multicycle path mean?

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cooldude040

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Can anyone tell me what is meant by multicycle path?? why do i need it ??
is it better to have multicycle path in my design or i should not exceed this limit( .sdc file will have this right) So when it goes to backend guy wt he has to do??
Explain me with the example...

Bye take care
 

Re: Multicycle path

A multicycle path describes a signal that is generated at one clock edge and is not used by the following circuitry until more than one clock period later. In other words, it is a signal that intentionally takes longer than a clock period to become stable.

The backend person needs to know this to set the timing constraints. The timing analyzer assumes that any signal generated by one flip flop and sampled by another will be used on the next clock cycle. Telling the timing analyzer that it will take longer than one clock to be used relaxes the timing on that signal and this helps close timing and prevent false timing errors.

Whether or not you need or have multicycle paths is up to you and your design.
 

Re: Multicycle path

The DFT guy will also want to know about your multicycle path, because ATPG has no knowledge of timing, it will generate patterns that assume that all paths resolve within the clock cycle. If the scan patterns are then simulated or run on the ATE, they will fail, unless they are run slower than your longest flop to flop path.

Most ATPG tools can read constraints files and generate better patterns, so it's not a problem, just something to watch out for. The same applies to false paths.

John

for DFT talk/info go to:
DFT Digest
DFT Forum
 

Re: Multicycle path

all static timing analysis tools assumes by default the flop to flop data transfer takes one clock cycle. u need explictly mention as mcp if it takes more than one clock cycle.
 

Multicycle path

MCP is purely dependent on your design nad please not tht there is no Limit for the no. of MCPs tht u can hv in ur design.

design scenarios where u can hv MCP

1) multiple clock domains ( i,e wen a signal is traversing frm a slower clock domain to a faster clock domain and vice-versa)

2) Multiplier/ divider logics bwtween 2 flops

these are the only 2 tht i kno. If ne1 knows more, Pls post it !!

WBR
Lakshman
 

Multicycle path

Without multi-cycle path, your timing constraint might get much tighter than you really need.
 

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