Who, when and where places spare cells?

[kumar_eee]

Can anyone answer me the following questions?

1. Who(RTL Desginer or Back-end Engr) will add the spare cells? My guess is RTL Designer.

2. Do we place spare cells during placement?

3. Does these cells placed at a particular location? If so, who will provide the location detail? Again my guess is front-end Designer

4. What about the input & output pins? Does these pins(Power & Signal) connected to something(VSS or VDD)?

 

[ljxpjpjljx]

Re: Spare Cells

for the question 3 ,I think backend engineer should discuss with frontend engineer!

 

[dementu666]

Re: Spare Cells

1. You can add spare cells in rtl and/or in Place&Route step! Either way is ok but you should discuss this with the designer (what kind of cells, how many, how/where to place them)!
2. The spare cells are placed in placement step. You should take care to mark them as spare cells or they will be removed by the tool as they are seen as redundant logic!
3. You can place the in specific location, spread them in a specified area or even spread them on the entire area of the digital!
4. The inputs are connected to VDD/VSS via STIE* cells! The outputs can be floating! Check spare cells handling specifics for the tool you are working with and if it does not have this you have to take care not to leave a floating input!

Hope this helps!

 

[mefirst1808]

Spare Cells

How to spread Spare cells over the specified area or entire tile....

 

[dementu666]

Re: Spare Cells

In ICC you can do this:

spread_spare_cells -bbox {{10.0 10.0} {100.0 200.0}} [get_cells spare*]

or:

create_bounds -rectangle {10 10 100 200} spare_module_name