what is the meaning of "footprint"

[owen_li]

Hi.

Can you tell me what is the meaning of "footprint" , in physical design ?

For example, if I have BUFX1, BUFX2, BUFX3, do these cells have the same

footprint?

Very glad to hear your comments. Thanks!

 

[cute_grass]

BUFX1, BUFX2, BUFX3 have the same footprint.

 

[poluekt]

Footprint for this cells - BUF.
This is name of cell without definition possible output load.

 

[kumar_eee]

You will be able to identify the cell type(inv or buf) using the footprint.

This will be very much useful when you try to automate some task and retrieve the result through some scripting(say tcl).

 

[flycar]

It mean a group have same function. When do OPT, could use the same footprint one for size up/down.

 

[koggestone]

for chips i worked on , footprint means standard cell layout x& y dimension and the corresponding input and output pin location.

for eg, some standard cells have same footprint to help in ECO mode timing fixing.

eg. flop and its mindelay version (that has bigger clk-to-q delay) may have same footprint for given size (eg flop_4x and flop_mindel_4x) . so once the layout of the block is done and maxtime is met , but u have hold time problem on that flop path, then u can replace that flop with mindelay version in the layout and u dont need to redo P&R .

similary buf_16x and buf_24x may have same footprint to fix maxtime without rerunning P&R .

similarily normal library and its LVT version of library will have same footprint to help in fixing setup time problems.

similarily normal library and its HVT version will have same footprint to decrease leakage in non critical path , and u can simply swap without rerunning P&R.

In more simple laymen terms, US Currency ( $1 bill, $5 bill , $20 bill,...) all have same footprint (to simplify Vending machines ,cash registers and ATM machines!! ), Whereas Indian Currency dont have same footprint and each bill denomination is of different size with different Colors!.