Native Flow Control Interface - 12.0 English

PG074 Aurora 64B/66B LogiCORE IP Product Guide

Document ID
PG074
Release Date
2022-10-19
Version
12.0 English

The Aurora 64B/66B protocol includes Native Flow Control (NFC) allowing receivers to control the rate at which data is sent by specifying the number of cycles during which the channel partner cannot send data. The data flow can even be turned off completely (XOFF) by requesting that the transmitter temporarily send only idles. NFC is typically used to prevent FIFO overflow conditions. This Figure and Table: Native Flow Control (NFC) Interface Ports detail the NFC port interface.

Figure 2-16: NFC Port Interface

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pg074_nfc_port_interface.jpg
Table 2-8: Native Flow Control (NFC) Interface Ports

Name

Direction

Clock Domain

Description

NFC_S_AXIS_TX

s_axi_nfc_tx_tvalid

Input

user_clk

Asserted (High) to request sending an NFC message to the channel partner. Must be held until s_axi_nfc_tx_tready is asserted.

s_axi_nfc_tx_tready

Output

user_clk

Asserted (High) when an Aurora 64B/66B core accepts an NFC request.

s_axi_nfc_tx_tdata[0:15] or s_axi_nfc_tx_tdata[15:0]

Input

user_clk

Incoming NFC message data from the channel partner.

For a detailed explanation of NFC operation, see the Aurora 64B/66B Protocol Specification (SP011) [Ref 9] .

Note: NFC completion mode is not applicable to streaming designs.

This Figure and This Figure show the NFC message format in big endian (default) and little endian modes.

Figure 2-17: NFC Message in Default Big Endian Mode

X-Ref Target - Figure 2-17

pg074_big_endian_nfc_message.jpg

Figure 2-18: NFC Message in Little Endian Mode

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pg074_little_endian_nfc_message.jpg

Note:

1. [n:0] bus format is used when the Little Endian support option is selected. [0:n] bus format is used when the Big Endian support option is selected. The core has an option to configure the AXI4-Stream User I/O as little endian from the Vivado IDE. The default is big endian.

2. Ports are active-High unless specified otherwise.