8101 datasheet(38/172 Pages) LSI

38 / 172 page

2-20

Functional Description

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.

8101 Datasheet(PDF) 38 Page - LSI Computer Systems