I haven't looked at Ethernet chips in detail, but they have similar analog circuitry. A "PHY" (physical layer) module does the analog encoding and decoding. St

I haven't looked at Ethernet chips in detail, but they have similar analog circuitry. A "PHY" (physical layer) module does the analog encoding and decoding. Standard cell libraries are lower-level than IP blocks since you're dealing with gates rather than functional units. I'm sure someone here knows about how they are licensed. On the chip I looked at, the analog module and the CPU were treated as IP blocks. These blocks were built by IBM so the intellectual property itself wasn't an issue. But the blocks were designed by other teams and essentially dropped onto the chip unchanged. For the revised version of the chip, they redesigned the logic but kept the original analog and CPU blocks.