LAN83C183 Datasheet, PDF (14/113 Pages) SMSC Corporation – FAST ETHERNET PHYSICAL LAYER DEVICE

1.1.2.1 100BASE-TX
In 100BASE-TX transmit operation, data is received on the Controller Interface from
an external Ethernet controller in the format shown in Figure 1.3 and Table 1.1. The
data is sent to the 4B5B encoder, which scrambles the encoded data. The scrambled
data is then sent to the TP transmitter. The TP transmitter converts the encoded and
scrambled data into MLT3 ternary format, preshapes the output, and drives the
twisted-pair cable.
TX_EN = 0
IDLE
PREAMBLE
PRMBLE
Figure 1.3 MII Frame Format
a. MII Frame Format
TX_EN = 1
Start
of
Frame
DATA Nibbles
TX_EN = 0
IDLE
SFD DATA 1 DATA 2 DATA N-1 DATA N
62 Bits
2 Bits
PREAMBLE = [ 1 0 1 0 ...] 62 Bits Long
SFD = [ 1 1 ]
DATAn = [Between 64−1518 Data Bytes]
IDLE = [TX_EN = 0]
First Bit
b. MII Nibble Order
MAC Serial Bit Stream
LSB D0
D1
D2
D3
D4
D5
D6
D7 MSB
First
Nibble
Second
Nibble
MII
Nibble
Stream
TXD0/RXD0
TXD1/RXD1
TXD2/RXD2
TXD3/RXD3
Table 1.1 Transmit Preamble and SFD Bits at MAC Nibble Interface
Signals
Bit Value
TXDO X X 1¹ 1 1 1 1 1 1 1 1 1 1 1 1 1 1² 1 D0³ D4⁴
TXD1 X X 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 D1 D5
TXD2 X X 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 D2 D6
TXD3 X X 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 D3 D7
TX_EN 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
1. 1st preamble nibble transmitted.
2. 1st SFD nibble transmitted.
3. 1st data nibble transmitted.
4. D0 through D7 are the first 8 bits of the data field.
In 100BASE-TX receive operation, the TP receiver takes incoming encoded and
scrambled MLT3 data from the twisted-pair cable, removes any high-frequency noise
from the input, equalizes the input signal to compensate for the effects of the cable,
performs baseline wander correction, qualifies the data with a squelch algorithm, and
converts the data from MLT3-encoded levels to internal digital levels. The output of
the receiver then goes to a clock and data recovery block that recovers a clock from
the incoming data, uses the clock to latch valid data into the device, and converts
the data back to NRZ format. The 4B5B decoder and descrambler then decodes and
unscrambles the NRZ data, respectively, and sends it out of the Controller Interface
SMSC DS – LAN83C183
14
Rev. 12/14/2000