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Chapter 5: IP Core Architecture
5–9
Physical Layer
June 2012
Altera Corporation
Stratix V Hard IP for PCI Express
■
Transaction Layer Packet Checker—This block checks the integrity of the received
TLP and generates a request for transmission of an ACK/NAK DLLP.
■
TX Arbitration—This block arbitrates transactions, prioritizing in the following
order:
a. Initialize FC Data Link Layer packet
b. ACK/NAK DLLP (high priority)
c. Update FC DLLP (high priority)
d. PM DLLP
e. Retry buffer TLP
f. TLP
g. Update FC DLLP (low priority)
h. ACK/NAK FC DLLP (low priority)
Physical Layer
The Physical Layer is the lowest level of the Stratix V Hard IP for PCI Express. It is the
layer closest to the link. It encodes and transmits packets across a link and accepts and
decodes received packets. The Physical Layer connects to the link through a
high-speed SERDES interface running at 2.5 Gbps for Gen1 implementations, at 2.5 or
5.0 Gbps for Gen2 implementations, and at 2.5, 5.0 or 8.0 Gbps for Gen 3
implementations.
The Physical Layer is responsible for the following actions:
■
Initializing the link
■
Scrambling/descrambling and 8B/10B encoding/decoding of 2.5 Gbps (Gen1),
5.0 Gbps (Gen2), or 128b/130b encoding/decoding of 8.0 Gbps (Gen3) per lane
■
Serializing and deserializing data
■
Operating the PIPE 3.0 Interface
■
Implementing auto speed negotiation (Gen2 and Gen3)
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Transmitting and decoding the training sequence
■
Providing hardware autonomous speed control
■
Implementing auto lane reversal