These cells (AON/LS/ISO/RET) are present in multi-power domain based designs.
- LS/ISO cells are to be placed at the power domain crossings.
- Placement of these cells can be done by the tool provided the secondary power routes are drawn at regular intervals through-out the design.
- Bounds/Inst Groups for these cells are created in case of non availability of secondary power routes through-out the design.
- AON cells are needed if the Always-On signal goes through the switchable region. If your design is congested and if you don’t want to pass these signals through the core logic then you can do the following:
- Create bounds for these cells around the edge of the switchable region for every x microns, here x is the max length that one AON cell can drive. This is if you don’t want these signals not to go through the core.
- Create islands for the AON power inside the switchable domain for every x microns, here x is the max length one buffer cell can drive. This is if you have congestion and area concerns.
- Finalize the RET cells placement after one placement trail, this is if you are creating a bound for these cells.
