set_max_capacitance and set_load

[energeticdin]

set_load

Hi,

Please explain me clearly
what is set_max_capacitance and set_load?

What is tthe diff between them?

Thanks
Din

 

[jbeniston]

set_max_capacitance

set_load - Sets the capacitance to a specified value on specified ports and nets in the current
design.
set_max_capacitance - Sets the max_capacitance attribute to a specified value on the specified ports and designs.

set_load is usually used to set what capacitance there is on an output (i.e. the external capacitance that exists and can't be changed)
set_max_capacitance sets the maximum capacitance that will be allowed on the specified net. If the tool calculates there is more capacitance than this limit, it will try to change the circuit to reduce the capacitance below this limit. Obviously it can't change the capacitance set by the set_load command, but it can change internal circuitry - by buffering, resizing cells etc.

 

[energeticdin]

set_load -wire_load

HI

Thanks.
for eg:
set_load 0.5 OUT1

On what basis, 0.5 pf constraints is loaded in SDC?
How we will come to know this value?

U r telling that set_load sets the capacitance to sp value on specified ports & nets and set_max_cap sets the max_captacitance to sp value on specified ports and design. Then it means both are setting capacitance value.

Why we need two different types of DC command?

thanks
Din