8101 Datasheet, PDF (38/172 Pages) LSI Computer Systems – Gigabit Ethernet Controller

Broadcast address filtering functions do not affect the reception of MAC
control frames. Other bits described in Section 2.17, “MAC Control
Frames,” control the reception of MAC control frames.
2.8.6 Reject or Accept All Packets
Setting the ACPTAL or REJALL bits in “Register 8–Configuration 2‚"
Section 4.3.9, programs the controller to accept or reject all packets
regardless of type or whether the packet passes the address filter.
These bits do not affect the reception of MAC control frames. Other bits
described in Section 2.17, “MAC Control Frames,” control the reception
of MAC control frames.
2.8.7 Frame Validity Checks
The receive MAC checks the following to determine the validity of each
receive packet:
• Valid FCS
• Oversize packet
• Undersize packet
Computing the CRC value on the incoming receive packet according to
IEEE 802.3 specifications and comparing it against the actual CRC value
in the FCS field of the received packet determines the validity of the FCS.
If the values are not the same, the frame is determined to be invalid and
the packet is discarded. Refer to Section 2.13, “Packet Discard” for more
information about discards. Clearing the DIS_CRC error bit in
“Register 8–Configuration 2‚" Section 4.3.9, programs the controller not
to discard a packet with a bad FCS.
Oversize packets are packets whose length is greater than the maximum
packet size. If a received packet is an oversize packet, then the packet
is determined to be invalid and is discarded. Refer to Section 2.13,
“Packet Discard” for more information about discards. Clearing the
DIS_OSIZE bit in “Register 8–Configuration 2‚" Section 4.3.9, programs
the controller not to discard an oversize packet and allow packets of
unlimited length.
2-20
Functional Description
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