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Chapter 5: Using the Client-side GMII Data Path

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_txd[7:0]preamble

gmii_tx_en

gmii_tx_er

SFD

FCS

Figure 5-2:GMII Error Propagation Within a Frame

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.

gmii_rxd[7:0]preamble

SFD

FCS

gmii_rx_dv

gmii_rx_er

Figure 5-3:GMII Normal Frame Reception

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Ethernet 1000BASE-X PCS/PMA or SGMII v9.1

 

 

UG155 March 24, 2008

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Xilinx 1000BASE-X manual Gmii Reception, Error Propagation, Normal Frame Reception, Using the Client-side Gmii Data Path