T71L6816A Taiwan Memory Technology, T71L6816A Datasheet - Page 6

• Manufacturer Part Number: T71L6816A
• Description: Sixteen-port 10/100 Switch
• Manufacturer: Taiwan Memory Technology

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3.4 Illegal Frames
The T71L6816A will check the errors of incoming frames and discard all illegal packets
if any non -recovered error found. The kinds of errors include FCS error, illegal packet
length, symbol error and dribble error. However, for preamble error, the T71L6816A will
try to identify the SFD even if the preamble error happened and the packet will be dropped
only if the T71L6808A can not well identify the incoming packet.
3.4.1 FCS Error
The T71L6816A will generate the 4 bytes of CRC checksum through every incoming packets
and compare the checksum with the FCS field to identify if the packet is corrupt or not.
If it is found that the CRC checksum is not matched with the FCS field, the T71L6816A
will discard this packet due to something wrong on data transmission.
3.4.2 Alignment Error
The T71L6816A will discard the packets with the frame length is of no n-integer in octet
unit. Exactly, the kind of such packet usually results in CRC checksum error and is called
as alignment error.
3.4.3 Dribble Error
Dribble error is that the packets contains some extra bit after four bytes of FCS. The
T71L6816A will drop those packets because those packets are usually similar to the FCS
error.
3.4.4 Length of Frames
The T71L6816A can recognize the legal frame with length ranges from 64 bytes to 1522
bytes including four bytes of FCS. Any packet with length smaller than 64 bytes or larger
than 1522 bytes will be discarded.
3.5 Frame Forwarding
The first six bytes(DA) and the second six bytes(SA) of every incoming packet received
by T71L6816A will be retrieved and passed to Address Resolution Logic unit(ARL). The ARL
will use the SA to update the address table and use the DA to determine which destination
port the packet should be forwarded to by address table lookup.
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Change to products or specifications without notice.
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P. 6
Preliminary T71L6816A
Publication Date:Jun. 2001
Revision:0.A