F-Tile Low Latency 50G Ethernet Intel® FPGA IP User Guide

ID 758946
Date 1/09/2024
Public

A newer version of this document is available. Customers should click here to go to the newest version.

Document Table of Contents

7.7. Flow Control Signals

Table 17.  Flow Control Interface
Signal Name Direction Width Description
pause_insert_tx0 Input QN 1

These signals are available only if Pause or PFC flow control support is synthesized. These indicates the MAC if a XON or XOFF Pause or PFC flow control frame should be sent.

FCQN (Flow Control Queue Number) = 1 for Pause

FCQN = 1 to 8 for PFC

The request for XON/XOFF flow control frame transmission can be done in either 1- or 2-bit request mode (see pause_insert_tx1).

1-bit mode request model:

  • 0 = No request
  • 0 to 1 = Generate XOFF request
  • 1 = Continue generate XOFF request
  • 1 to 0 = Generate XON request

2-bit mode request model:

Represents the lower bit. Only takes effect when the CSR of 2-bit Flow Control Request mode selects “Signal”.

  • 00 = No request
  • 01 = XON request
  • 10 = XOFF request
  • 11 = Invalid
pause_insert_tx1 Input QN 1

Use in conjunction with pause_insert_tx0 to form a 2-bit request for XON/XOFF flow control frame transmission. This represents the upper bit of the 2-bit control.

pause_receive_rx Output QN 1 Asserted to indicate an RX pause signal match. The IP core asserts bit [n] of this signal when it receives a pause request with an address match, to signal the TX MAC to throttle its transmissions from priority queue [n] on the Ethernet link.
1 QN means queue number.