User guide

In serialize x4 mode, the byte serializer serializes 32-bit data into 8-bit data. As the parallel data width
from the TX FIFO is divided four times, the clock rate is quadrupled.
After byte serialization, the byte serializer forwards the least significant word first followed by the most
significant word. For example, if the FPGA fabric-to-PCS Interface width is 32, the byte serializer
forwards tx_parallel_data[7:0] first, followed by tx_parallel_data[15:8],
tx_parallel_data[23:16] and tx_parallel_data[31:24].
Related Information
PCI Express (PIPE) on page 2-228
For more information about using the Serialize x4 mode in the PCIe protocol.
8B/10B Encoder
The 8B/10B encoder takes in 8-bit data and 1-bit control as input and converts them into a 10-bit output.
The 8B/10B encoder automatically performs running disparity check for the 10-bit output. Additionally,
the 8B/10B encoder can control the running disparity manually using the tx_forcedisp and tx_dispval
ports.
Figure 5-39: 8B/10B Encoder Block Diagrams
8B/10B Encoderdataout[9:0]
To the Serializer
datain[7:0]
tx_datak
tx_forcedisp
tx_dispval
From the Byte Serializer
When the PCS-PMA Interface Width is 10 bits
8B/10B Encoder
dataout[19:10]
To the Serializer
datain[15:8]
tx_datak[1]
tx_forcedisp[1]
tx_dispval[1]
From the Byte Serializer
dataout[9:0]
datain[7:0]
tx_datak[0]
tx_forcedisp[0]
tx_dispval[0]
MSB
Encoding
LSB
Encoding
When the PCS-PMA Interface Width is 20 bits
When the PCS-PMA interface width is 10 bits, one 8B/10B encoder is used to convert the 8-bit data into a
10-bit output. When the PCS-PMA interface width is 20 bits, two cascaded 8B/10B encoders are used to
convert the 16-bit data into a 20-bit output. The first eight bits (LSByte) is encoded by the first 8B/10B
encoder and the next eight bits (MSByte) is encoded by the second 8B/10B encoder. The running disparity
of the LSByte is calculated first and passed on to the second encoder to calculate the running disparity of
the MSByte.
Note:
You cannot enable the 8B/10B encoder when the PCS-PMA interface width is 8 bits or 16 bits.
5-40
8B/10B Encoder
UG-01143
2015.05.11
Altera Corporation
Arria 10 Transceiver PHY Architecture
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