regarding multicycle and false paths

hi everyone,


can ant one explain multi cycle paths and false paths very clearly ?

at what cases these paths will occur ?

what r the advantages and disadvantages ...


if anyone have material plz upload material ..

regards
mallikarjun

hi,

A false path is an async path in a logic design that may be valid at any time, irrespective of clock reference.

A false path can cause a lot of timing analysis issues if it is not handled correctly.
If a false path exist in a design and is not configured during synthesis, the synthesis tool may try to optimize this path.

Most synthesis tools have its own set of command to disable false path.
Example of false path: Reset signal

Multicycle paths are paths have its propagation delay more than one clock cycle

Multicycle paths must also be configured during synthesis to ensure the synthesis tool does not try to optimize the path into a single clock cycle.

Example of multicycle path: In between 2 flip flop, a combinational logic has a delay more than 1 clock cycle.

Hope it helps,

check out this link
https://www.vlsichipdesign.com/static timing analysis

Which explains scenarios when a false path and multiple scenarios to explain about multicycle path is well explained with diagrams..

best regards,
vlsichipdesigner
www.vlsichipdesign.com

Multicycle paths are paths between registers that intentionally take more
than one clock cycle to become stable. For example a register may need to
trigger a signal every second or third rising clock edge.

A False path is any path that is not relevant to a circuit's operation.false paths are paths in a design which are functionally never be true.For eg ,Paths between any two asynchronous clocks. The designer here knows such path can never be true .

Hi These both topics comes under DC.
Multicycle path is a timing path which is not expected to propagate a signal in one cycle.
Set Multicycle paths to DC to allow multiple clock cycles for data to propagate along a path

Dinesh

both r timing exceptions n further these are applied only when delay of combo logic is more than clock period !!
shiv

read this ppt for detailed analysis of false path

False path is a logic path in design that exists but should not be analyzed for timing .
It tell DC to ignore the timing constraints on certain paths
Useful for constraining asynchronous paths & logically false paths.
Declaring a path to be false removes all timing constraints from the path.
It still calculates the path delay, but does not report it to be an error, no matter how long or short the delay.
It sets point-to-point timing exception on a path that meet the criterial u specify such as “from” and “to” points.

Dinesh

simply:
multi-cycle path--->we need analyze timing but should over one clock cycle
false path ---->we don't concern its timing.