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April, 2002
L84302 Quad 4-Port Ethernet Controller - Technical Manual
Copyright 1997-2002 by LSI Logic Corporation. All rights reserved.
first 56-bits of 1’s and 0’s are considered to be the preamble, and the last
8-bits of 10101011 are considered to be the SFD (Start of Frame
Delimiter).
3.2.3 Destination Address
The destination address is a 48-bit field containing the address of the
station(s) to which the frame is directed. The format of the address field
is the same as defined in IEEE 802.3 and shown in part b. of
Figure 3
.
The destination address can be either a unicast address to a specific
station, a multicast address to a group of stations, or a broadcast
address to all stations. The first and second bits determine whether an
address is unicast, multicast or broadcast, and the remaining 46-bits are
the actual address bits, as shown in part b. of
Figure 3
.
3.2.4 Source Address
The source address is a 48-bit field containing the specific station
address from which the frame originated. The format of the address field
is the same as defined in IEEE 802.3 and shown in part b. of
Figure 3
.
3.2.5 Length/Type Field
The 16-bit length/type field takes on the meaning of either packet length
or packet type, depending on its numeric value, as described in
Table 1
.
3.2.6 Data
The data is a 46-1500 byte field containing the actual data to be
transmitted between two stations. If the actual data is less than 46 bytes,
extra 0’s are added to increase the data field to the 46-byte minimum.
Adding these extra 0’s is referred to as padding.
Table 1
Length/Type Field Definition
Length/Type Field Value (Decimal)
Length or Type
Definition
0-1500
Length
Total number of bytes in data field, minus
any padding.
1501-1517
Neither
Undefined
>=1518
Type
Frame type