Abstracts for Routed Blocks with Power Rings

There might be situations in which the cell data imported comes from a DEF file. This is usually a routed block for which you might want to create an abstract to use at a higher level of a design.

Abstract Generator can generate abstracts from routed blocks. This includes the ability to create abstracts for blocks with ring power pins, for blocks with cover blockages inside the power ring, and for blocks with detailed obstructions for signal nets crossing the power rings.

Power Pins

Consider the following points when deciding which approach to use when dealing with power ring pins:

Before you decide whether or not power extraction is necessary.
Power extraction is not required after running the Pins step, if the power pins contain at least the power pin geometry. They will contain power pin geometry if the power ring shapes were defined as physical pins in the imported DEF file. This is unlikely, and in the case where no physical pins were defined in the DEF file, the Pins step will create pins from all of the power routing in the block (including the power ring).
If extraction is required, perform a limited power extraction by limiting the hierarchy depth. This will result in the extraction of the power ring plus some other top level shapes. As a recommendation, set extraction depth to 1 so that Abstract Generator finds the ring pins plus the via geometry. Go to step 2.
If there is no need to extract, leave power extraction turned off and consider the Abstract step requirements in step 2.
In the Abstract step, ensure that the Create ring pins option is turned on. The algorithm to determine if a power pin should be preserved as a ring pin is based on distance to boundary. The closest power pin to the boundary is selected along with any others that are equidistant. Therefore, if a power ring is equidistant to the boundary on all sides, then everything should be fine.
Otherwise, you will have to manually control the settings in the Ring pin max distance to boundary field, setting it to be equal to the maximum distance from the boundary within which you want any power shapes to be considered as ring pins.
You must set this based on the distance to the inner ring (VDD or VSS, whichever is inner).

Signal Pins

If the signal pins read in from the DEF file are sufficient, there is no need to perform connectivity extraction, and no requirement to have boundary pins turned on. Therefore, turn he Create boundary pins option off since it is on by default in the Block bin.

Alternatively, if your signal pins are insufficient, you would run connectivity extraction and leave the Create boundary pins option turned on.

Obstructions

To form the necessary obstructions with the region inside the power ring as a solid obstruction and with the signals that cross the ring into obstructions in that region, set the Blockage option to Cover in the Layer Assignment for Blockages table and specify the cover blockage distance to boundary value.

Virtuoso Abstract Generator User Guide
Product Version IC23.1, November 2023