R-Tile Avalon® Streaming Intel® FPGA IP for PCI Express* User Guide

ID 683501
Date 12/04/2023

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4.4.4. Deskew Signals

In PIPE Direct mode, the R-Tile Avalon Streaming Intel FPGA IP for PCI Express removes any lane-to-lane skew introduced while crossing the EMIB. A dedicated deskew marker is used for detecting and compensating for any multi-lane skew introduced by EMIB. The deskew logic can account for a maximum of up to 3 cycles of parallel skew. After a cold/warm/hot reset or CvP update, the deskew process will start.

The user application logic needs to send a deskew marker every 16 clock cycles for the purpose of deskewing the data on the EMIB channels. The R-Tile Avalon Streaming Intel FPGA IP for PCI Express runs the deskew process every time it receives the deskew marker.

Table 84.  EMIB TX Deskew Grouping for R-Tile Topologies
PIPE Direct Tx Deskew Bundle Octet 1 Octet 0
Lane 15 Lane 14 Lane 13 Lane 12 Lane 11 Lane 10 Lane 9 Lane 8 Lane 7 Lane 6 Lane 5 Lane 4 Lane 3 Lane 2 Lane 1 Lane 0
1X16 Octet1_Dsk_0 Octet0_Dsk_0
2X8 Octet1_Dsk_0 Octet0_Dsk_0
4X4 Octet1_Dsk_2 Octet1_Dsk_0 Octet0_Dsk_2 Octet0_Dsk_0
8X2 Octet1_Dsk_3 Octet1_Dsk_2 Octet1_Dsk_1 Octet1_Dsk_0 Octet0_Dsk_3 Octet0_Dsk_2 Octet0_Dsk_1 Octet0_Dsk_0
16X1 No Tx Deskew
2X4; 1X8 Octet1_Dsk_2 Octet1_Dsk_0 Octet0_Dsk_0
4X2; 1X8 Octet1_Dsk_3 Octet1_Dsk_2 Octet1_Dsk_1 Octet1_Dsk_0 Octet0_Dsk_0
8X1; 1X8 No Tx Deskew Octet0_Dsk_0
1X8; 2X4 Octet1_Dsk_0 Octet0_Dsk_2 Octet0_Dsk_0
4X2; 2X4 Octet1_Dsk_3 Octet1_Dsk_2 Octet1_Dsk_1 Octet1_Dsk_0 Octet0_Dsk_2 Octet0_Dsk_0
8X1; 2X4 No Tx Deskew Octet0_Dsk_0 Octet0_Dsk_0
1X8; 4X2 Octet1_Dsk_0 Octet0_Dsk_3 Octet0_Dsk_2 Octet0_Dsk_1 Octet0_Dsk_0
2X4; 4X2 Octet1_Dsk_2 Octet1_Dsk_0 Octet0_Dsk_3 Octet0_Dsk_2 Octet0_Dsk_1 Octet0_Dsk_0
8X1; 4X2 No Tx Deskew Octet0_Dsk_3 Octet0_Dsk_2 Octet0_Dsk_1 Octet0_Dsk_0
1X8; 8X1 Octet1_Dsk_0 No Tx Deskew
2X4; 8X1 Octet1_Dsk_2 Octet1_Dsk_0 No Tx Deskew
4X2; 8X1 Octet1_Dsk_3 Octet1_Dsk_2 Octet1_Dsk_1 Octet1_Dsk_0 No Tx Deskew