The previous chapter described:

The logical Physical Layer core logic and how an outbound packet is processed before clocking the packet out differentially.
How an inbound packet arriving from the Link is processed and sent to the Data Link Layer.
Sub-block functions of the Physical Layer such as Byte Striping and un-striping logic, Scrambler and De-Scrambler, 8b/10b Encoder and decoder, Elastic Buffers and more.