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generally set_drive is used to specify the driving strength of an output for ex: set_drive 0 for clocks and reset
set_driving_cell is set on inputs to specify the input side driving cell.
Hi
set_drive is used to specify the drive strength / driving resistence of an object.
for e.g. set_drive 0 clk indicates 0 drive resistence for clk --> infinite drive strength (0 transition times etc).
whereas set_driving strength is used to specify a particular technology library cell used for driving a port/pin. All the calculations related to transition times, delays etc are done with thye characteristics of the driving_cell.
hi,nittinsharma80
can u tell me how the dc translate the set_drive or set_driving_cell to get their characteristic to calculate the transition time on the input pin?
That is how the resistence of input pin translate to the transition time and how the driving cell get which characteristic translated to the transition time?
thank u
The set_driving_cell command specifies that the driving characteristics of the specified cell should be used for delay calculation. By default, a zero transition time is used to stimulate the driving cell arcs. Options are available to control which cell input pin and what input transition should be used to stimulate the driving cell. The portion of the driving cell delay caused by the net will be included as a port delay on the input port.
set_driving_cell is the preferred method for specifying the drive characteristics of an input port, especially in a PrimeTime SI analysis.
thanku u,no_mad!
that means the driving_cell will use a default zero input transtion to calculate his output transition which used as the input transition of the input pin of the design.
i still can't understanding this:
The portion of the driving cell delay caused by the net will be included as a port delay on the input port.
before layout we will set_input_delay on the input pin of the design,after layout still work?or it will override the net'RC delay on the input pin?
how about set_drive?i still unknow how to use the set_drive to get the input transition of input pin.
best regard
that means the driving_cell will use a default zero input transtion to calculate his output transition which used as the input transition of the input pin of the design.
Bendrift, dont get it wrong. I said by default, a zero transition time is used to stimulate the driving cell arcs.
Ok, I thing this might help you.
set_drive
to set the drive resistance on the top level ports of the design when the input port drive capability cannot be characterized with a cell in the technology library.
But this command is not as accurate as accurate for nonlinear delay models as the set_driving_cell command.
set_driving_cell
to specify drive characteristic on ports that are driven by cells in the technology library.
set_drive and set_driving_cell are used at the input ports of the block.
set_drive command is used to specify the drive strength at the input port.
It is typically used to model the external drive resistance to the ports of
the block or chip. The value of 0 signifies highest drive strength and is
commonly utilized for clock ports. Conversely, set_driving_cell is used
to model the drive resistance of the driving cell to the input ports. This
command takes the name of the driving cell as its argument and applies
all design rule constraints of the driving cell to the input ports of the
block. --from advanced chip synthesis
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