Native Flow Control Interface

Native Flow Control Interface - 11.1 English

Aurora 8B/10B LogiCORE IP Product Guide (PG046)

Document ID

PG046

Release Date

2023-10-19

Version

11.1 English

The NFC interface is created when the core is generated with the NFC option enabled. This interface includes a request (s_axi_nfc_tx_tvalid) and an acknowledge (s_axi_nfc_tx_tready) port that are used to send NFC messages, and a 4-bit s_axi_nfc_tx_tdata port to specify the number of idle cycles requested.

Table: NFC I/O Ports lists the ports for the NFC interface available only in full-duplex Aurora 8B/10B cores.

Table 2-10: NFC I/O Ports
Name	Direction	Clock Domain	Description
NFC_S_AXIS_TX
s_axi_nfc_tx_tready	Output	user_clk	Asserted when the core accepts an NFC request.
s_axi_nfc_tx_tdata[0:3] or s_axi_nfc_tx_tdata[3:0]	Input	user_clk	Indicates the number of PAUSE idles the channel partner must send when it receives the NFC message. Must be held until s_axi_nfc_tx_tready is asserted.
s_axi_nfc_tx_tvalid	Input	user_clk	Asserted to request an NFC message be sent to the channel partner. Must be held until s_axi_nfc_tx_tready is asserted.
NFC_M_AXIS_RX
m_axi_nfc_tx_tvalid	Output	user_clk	Indicates an NFC message is received from the partner.
m_axi_nfc_tx_tdata[0:3] or m_axi_nfc_tx_tdata[3:0]	Output	user_clk	Indicates the PAUSE value of the received NFC message. This port should be sampled with m_axi_nfc_tx_tvalid.

Table: NFC Codes shows the codes for native flow control (NFC). These values are driven on bits [0:3] for big endian format and [3:0] for little endian format.

Table 2-11: NFC Codes
s_axi_nfc_tx_tdata	Idle Cycles Requested
0000	0 (XON)
0001	2
0010	4
0011	8
0100	16
0101	32
0110	64
0111	128
1000	256
1001 to 1110	Reserved
1111	Infinite (XOFF)

The user application asserts s_axi_nfc_tx_tvalid and writes an NFC code to s_axi_nfc_tx_tdata. The NFC code indicates the minimum number of idle cycles the channel partner should insert in its TX data stream. The user application must hold s_axi_nfc_tx_tvalid and s_axi_nfc_tx_tdata until s_axi_nfc_tx_tready is asserted. Aurora 8B/10B cores cannot transmit data while sending NFC messages. s_axi_tx_tready is always deasserted on the cycle following an s_axi_nfc_tx_tready assertion.