Posted by Godwin Maben on February 19, 2009
In addition to various structural checks, we saw in last few posts. We also need to look at PG structure of the design as well. Here are few things in the PG that a structural check can help us in finding
(1) Cross-Domain PG shorts
(2) Special Cells PG connections
(3) Back-up/Internal/Primary Power hookups
(4) Floating PG nets
(5) Incorrect placement of cells based on the PG structure ….etc
In one of my recent engagements, we figured out that, from an implementation perspective pg connections may seem right, but actually if you look at the top level and validate using Golden UPF, these connections may be wrong. One example of that is, let’s take 3 inverters connected back to back, if one inverter in the middle is supposed to be connected to say VDD1, but actually connected to VDD2. Now in the implementation domain most of the pg checks would say this is ok, because the source and sink PG may be connected to VDD2!!!!!.
Let me sign-off for now and talk more about it in my later posts.
- Godwin Maben