Achronix Speedster22i SerDes - Manual (Page 16)

PCS Blocks in the Transmitter (TX)
This section presents the transmitter (TX) data path within a PCS. The key blocks within the
SerDes transmitter are:
• Encoder: Encodes the data for transmission line. Primary goal is to ensure DC
balance by eliminating long sequence of 1’s or 0’s.
• Polarity Bit Reversal (PBR): Inverts the polarity of data and ordering of data to be
transmitted.
The building block for the SerDes IP is the 1 lane configuration. A simplified block diagram
of the TX data path is shown in Figure 6: - PCS Transmitter Block Overview . The functional
blocks shown in the diagram represent the functionality supported by a single SerDes lane. A
summary of the supported standards is covered in “Table 1 – SerDes Standards”.
Figure 6: PCS Transmitter Block Overview
* SerDes configured in Generic mode supports only 8b/10b encoding.
** Either of PBR#0 or PBR#1 can be used or both may be bypassed.
Note: The PCS block will support lane-bonding across multiple SerDes lanes (max 12)
Chapter – “Design Flow: Creating a SerDes Design” presents the ground-up steps that can be
followed to prepare a design that supports lane-bonding.
The PCS blocks on TX path are detailed below.
PCS Self Test Logic
This block generates transmit data for PCS self test, detailed in “PCS Test Pattern Generator”
and “PCS Test Pattern Checker”.
Polarity bit reversal (PBR) #0 and #1
This block can invert the polarity of the incoming data. It can also reverse the bits of the
incoming data such that effectively the most significant bit is sent first, rather than the least
significant bit (default). For 16/20bit (2 words) bit streams, the word order can also be
inverted such that effectively the most significant byte is sent first, rather than the least
significant byte (default).
There are two PBR blocks on transmission data path, as shown in “Figure 6: PCS Transmitter
Block Overview”. PBR0 is used before the protocol encapsulation block and PBR1 is used on
encoded data. Either PBR0 or PBR1 can be used. Alternatively, both of these two blocks can
be bypassed.
16 UG028, July 1, 2014