Xilinx 1000BASE-X - Manual (Page 54)

54 www.xilinx.com Ethernet 1000BASE-X PCS/PMA or SGMII v9.1
UG155 March 24, 2008
Chapter 5: Using the Client-side GMII Data Path R
Error Propagation
A corrupted frame transfer is illustrated in Figure 5-2 . An error may be injected into the
frame by asserting gmii_tx_er at any point during the gmii_tx_en assertion window.
The core ensures that all errors are propagated through both transmit and receive paths so
that the error is eventually detected by the link partner.
GMII Reception
This section includes figures that illustrate GMII reception. In these figures the clock is not
labelled. The source of this clock signal will vary, depending on the options used when the
core is generated. For more information on clocking, see Chapters 6, 7 and 8.
Normal Frame Reception
The timing of normal inbound frame transfer is illustrated in Figure 5-3 . This shows that
Ethernet frame reception is proceeded by a preamble field. The IEEE 802.3 specification
(see clause 35) allows for up to all of the seven preamble bytes that proceed the Start of
Frame Delimiter (SFD) to be lost in the network. The SFD will always be present in well-
formed frames.
Figure 5-2: GMII Error Propagation Within a Frame
gmii_txd[7:0]
gmii_tx_en
gmii_tx_er
preamble FCS
SFD
Figure 5-3: GMII Normal Frame Reception
gmii_rxd[7:0]
gmii_rx_dv
gmii_rx_er
preamble FCS
SFD