LXT972 Level One, LXT972 Datasheet - Page 21

• Manufacturer Part Number: LXT972
• Description: 3.3V Dual-Speed Fast Ethernet Transceiver Datasheet
• Manufacturer: Level One

100 Mbps Operation
100BASE-X Network Operations
During 100BASE-X operation, the LXT972 transmits and
receives 5-bit symbols across the network link.
shows the structure of a standard frame packet. When the
MAC is not actively transmitting data, the LXT972 sends
out Idle symbols on the line.
Figure 12: 100BASE-X Frame Format
.
R e p l a c e d b y
/J/K/ code-groups
Start-of-Stream
Delimiter (SSD)
P 0
64-Bit Preamble
P 1
(8 Octets)
P 6
Delimiter (SFD)
Start-of-Frame
S F D
D A
Address (6 Octets each)
Destination and Source
D A
S A
Figure 12
S A
P a c k e t L e n g t h
L 1
(2 Octets)
L 2
In 100TX mode, the LXT972 scrambles and transmits the
data to the network using MLT-3 line code
page
descrambled, decoded, and sent across the MII to the
MAC.
(Pad to minimum packet size)
22). MLT-3 signals received from the network are
D 0
Data Field
D 1
LXT972 Functional Description
D n
Frame Check Field
(4 Octets)
C R C
End-of-Stream Delimiter (ESD)
/T/R/ code-groups
R e p l a c e d b y
InterFrame Gap / Idle Code
I0
(> 12 Octets)
(Figure 13 on
IFG
21