Inc. Network Card User Manual

1-Gigabit Ethernet MAC v8.5 User Guide www.xilinx.com 53
UG144 April 24, 2009
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Chapter 6
Using Flow Control
This chapter describes the operation of the flow-control logic of the GEMAC core. The flow
control block is designed to clause 31 of the IEEE 802.3-2005 standard. The MAC may be
configured to transmit pause requests and to act on their reception; these modes of
operation can be independently enabled or disabled. See “Flow Control Configuration,”
on page 81.
Overview of Flow Control
Flow Control Requirement
Figure 6-1 illustrates the requirements for Flow Control.
Figure 6-1: Requirement for Flow Control
User MAC
FIFO
Client Logic
Tx
Rx
Link Partner MAC
Tx
Rx
125MHz -100ppm
125MHz +100ppm
Application
User System