Arria® V Device Handbook: Volume 2: Transceivers

ID 683573
Date 5/29/2020
Public
Document Table of Contents

1.2.3.2.9. Receiver FIFO

The receiver FIFO block operates in different modes based on the transceiver datapath configuration.

The Quartus II software automatically selects receiver FIFO mode for the configuration you use.

Clock Compensation Mode

The receiver FIFO is configured in clock compensation mode for the 10GBASE-R configuration. In clock compensation mode, the FIFO deletes idles or ordered sets and inserts only idles to compensate up to a ±100 ppm clock difference between the remote transmitter and the local receiver.

Generic Mode

The receiver FIFO is configured in generic mode for the Interlaken configuration. In generic mode, the receiver FIFO provides the FIFO partially empty and FIFO full status signals to the FPGA fabric to control the read side of the FIFO.

Phase Compensation Mode

The receiver FIFO is configured in phase compensation mode for the 10G custom configuration. In phase compensation mode, the FIFO compensates for the phase difference between the FIFO write clock and the read clock.

XAUI Mode

In XAUI mode, the receiver FIFO compensates for up to ±100 ppm (200 ppm total) difference between the upstream transmitter and the local receiver reference clock. The XAUI protocol requires the transmitter to send /R/ (/K28.0/) code groups simultaneously on all four lanes (denoted as ||R|| column) during inter-packet gaps (IPGs), conforming to the IEEE P802.3ae specification. The receiver FIFO operation in XAUI mode is compliant with the IEEE P802.3ae specification.

PCIe Mode

In PCIe mode, the receiver FIFO compensates for up to ±300 ppm (total 600 ppm) difference between the upstream transmitter and the local receiver. The PCIe protocol requires the transmitter to send SKP ordered sets during IPGs, conforming to the PCIe base specification 2.0. The SKP ordered set is defined as a /K28.5/ COM symbol followed by three consecutive /K28.0/ SKP symbol groups.

The PCIe protocol requires the receiver to recognize a SKP ordered set as a /K28.5/ COM symbol followed by one to five consecutive /K28.0/ SKP symbols. The rate match FIFO operation is compliant with PCIe Base Specification 2.0.