Altera 10-Gbps Ethernet MAC MegaCore Function - Manual (Page 84)

Chapter 7: Functional Description 7–17
Congestion and Flow Control
February 2014 Altera Corporation 10-Gbps Ethernet MAC MegaCore Function User Guide
If pause frame transmission is triggered when the MAC is generating a pause
frame, the MAC ignores the incoming request and completes the generation of the
pause frame. Upon completion, if the avalon_st_pause_data signal remains
asserted, the MAC generates a new pause frame and continues to do so until the
signal is deasserted.
1 Assert the avalon_st_pause_data signal for at least 1 TX clock cycle
(tx_tx_clk) for the MAC to generate the pause frame right after the current
transmitting packet.
■ tx_pauseframe_control register—A host (software) can set this register to trigger
pause frames transmission. Setting tx_pauseframe_control[1] to 1 triggers the
transmission of XOFF pause frames; setting tx_pauseframe_control[0] to 1
triggers the transmission of XON pause frames. The register clears itself after the
request is executed.
You can configure the pause quanta in the tx_pauseframe_quanta register. The
MAC sets the pause quanta field in XOFF pause frames to this register value.
1
The tx_pauseframe_control register takes precedence over the
avalon_st_pause_data
signal.