BCM89359 Advance Data Sheet
PCI Express Interface
Transaction Layer Interface
The PCIe core employs a packet-based protocol to transfer data between the host and BCM89359 device,
delivering new levels of performance and features. The upper layer of the PCIe is the transaction layer. The
transaction layer is primarily responsible for assembly and disassembly of transaction layer packets (TLPs). TLP
structure contains header, data payload, and end-to-end CRC (ECRC) fields, which are used to communicate
transactions, such as read and write requests and other events.
A pipelined full split-transaction protocol is implemented in this layer to maximize efficient communication
between devices with credit-based flow control of TLP, which eliminates wasted link bandwidth due to retries.
Data Link Layer
The data link layer serves as an intermediate stage between the transaction layer and the physical layer. Its
primary responsibility is to provide reliable, efficient mechanism for the exchange of TLPs between two directly
connected components on the link. Services provided by the data link layer include data exchange, initialization,
error detection and correction, and retry services.
The data link layer packets (DLLPs) are generated and consumed by the data link layer. DLLPs are the
mechanism used to transfer link management information between data link layers of the two directly connected
components on the link, including TLP acknowledgement, power management, and flow control.
Physical Layer
The physical layer of the PCIe provides a handshake mechanism between the data link layer and the high-speed
signaling used for Link data interchange. This layer is divided into the logical and electrical functional subblocks.
Both subblocks have dedicated transmit and receive units that allow for point-to-point communication between
the host and BCM89359 device. The transmit section prepares outgoing information passed from the data link
layer for transmission, and the receiver section identifies and prepares received information before passing it to
the data link layer. This process involves link initialization, configuration, scrambler, and data conversion into a
specific format.
Logical Subblock
The logical sub block primary functions are to prepare outgoing data from the data link layer for transmission
and identify received data before passing it to the data link layer.
Scrambler/Descrambler
This PCIe PHY component generates pseudo-random sequence for scrambling of data bytes and the idle
sequence. On the transmit side, scrambling is applied to characters prior to the 8b/10b encoding. On the receive
side, descrambling is applied to characters after 8b/10b decoding. Scrambling may be disabled in polling and
recovery for testing and debugging purposes.
Broadcom®
September 9, 2014 • 89359-DS100-R
Page 62
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