5–10
Chapter 5: IP Core Architecture
Physical Layer
Arria V GZ Hard IP for PCI Express
November 2012
Altera Corporation
illustrates the Physical Layer architecture.
The Physical Layer is subdivided by the PIPE Interface Specification into two layers
(bracketed horizontally in
■
Media Access Controller (MAC) Layer—The MAC layer includes the LTSSM and
the scrambling/descrambling and multilane deskew functions.
■
PHY Layer—The PHY layer includes the 8B/10B and 128b/130b encode/decode
functions, elastic buffering, and serialization/deserialization functions.
The Physical Layer integrates both digital and analog elements. Intel designed the
PIPE interface to separate the MAC from the PHY. The Arria V GZ Hard IP for PCI
Express compiles with the PIPE interface specification.
The PHYMAC block is divided in four main sub-blocks:
■
MAC Lane—Both the RX and the TX path use this block.
■
On the RX side, the block decodes the Physical Layer Packet and reports to the
LTSSM the type and number of TS1/TS2 ordered sets received.
■
On the TX side, the block multiplexes data from the DLL and the LTSTX
sub-block. It also adds lane specific information, including the lane number
and the force PAD value when the LTSSM disables the lane during
initialization.
Figure 5–5. Physical Layer
Scrambler
8B10B
Encoder
Lane n
TX+ / TX-
Scrambler
8B10B
Encoder
Lane 0
TX+ / TX-
Descrambler
8B10B
Decoder
Lane n
RX+ / RX-
Elastic
Buffer
LTSSM
State Machine
SKIP
Generation
Control & Status
PIPE
Emulation Logic
Link Ser
ializ
er
for an x
8
Link
TX Packets
RX MAC
Lane
De
v
ice
T
ranscei
v
er (per Lane)
w
ith 2.5 or 5.0 G
b
ps SERDES & PLL
Descrambler
8B10B
Decoder
Lane 0
RX+ / RX-
Elastic
Buffer
RX MAC
Lane
PIPE
Interface
M
u
ltilane Desk
e
w
Link Ser
ializ
er f
or an x
8
Link
RX Packets
Transmit
Data Path
Receive
Data Path
MAC Layer
PHY layer
To Link
To Data Link Layer