JESD204C Intel® FPGA IP User Guide

ID 683108
Date 2/10/2023
Public

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3.4. Scrambler/Descrambler

Both the scrambler and descrambler are designed in a 128-bit parallel implementation and the scrambling/descrambling order starts from the first octet with MSB first.
Figure 4. Scrambling/Descrambling Order

The JESD204C TX and RX IP core support scrambling by implementing a 128-bit parallel scrambler in each lane. The scrambler and descrambler are located in the JESD204C IP MAC interfacing to the Avalon® streaming interface. You can enable or disable scrambling through CSR configuration for all lanes. Mixed mode operation, where scrambling is enabled for some lanes, is not permitted.

The scrambling polynomial is:

x58 + x39 + 1

The descrambler can self-synchronize in 58 bits. In a typical application where the reset value of the scrambler seed is different from the converter device to FPGA logic device, the correct user data is recovered in the receiver in 1 link clock (due to the 128-bit architecture). The PRBS pattern checker on the transport layer should always disable checking of the first eight octets from the JESD204C RX IP.