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Receiving Inbound Frames

R

Frame Reception with Errors

Figure 5-2illustrates an unsuccessful frame reception (for example, a fragment frame or a frame with an incorrect FCS). In this case, the rx_bad_frame signal is asserted to the client at the end of the frame. It is then the responsibility of the client to drop the data already transferred for this frame.

The following conditions cause the assertion of rx_bad_frame:

FCS errors occur.

Packets are shorter than 64 bytes (undersize or fragment frames).

Jumbo frames are received when jumbo frames are not enabled.

VLAN frames of length 1519-1522 are received when VLAN frames are not enabled.

A value of 0x0000 to 0x002D is in the type/length field. In this situation, the frame should be padded to minimum length. If it is not padded to exactly minimum frame length, the frame is marked as bad (when length/type checking is enabled).

A value of 0x002E to 0x0600 is in the type/length field, but the real length of the received frame does not match this value (when length/type checking is enabled).

Any control frame that is received is not exactly the minimum frame length (unless control frame length checks are disabled).

gmii_rx_er is asserted at any point during frame reception.

An error code is received in the 1-Gigabit frame extension field.

A valid pause frame, addressed to the MAC, is received when flow control is enabled. Please see “Overview of Flow Control,” on page 53.

gmii_rx_clk

rx_data[7:0]

DA SA L/T DATA

rx_data_valid

rx_good_frame

rx_bad_frame

Figure 5-2:Frame Reception with Error

1-Gigabit Ethernet MAC v8.5 User Guide

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UG144 April 24, 2009

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Xilinx UG144 manual Frame Reception with Errors, Receiving Inbound Frames

UG144 specifications

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