SMSC LAN91C111 - Manual (Page 26)

10/100 Non-PCI Ethernet Single Chip MAC + PHY
Datasheet
Revision 1.91 (08-18-08) 26 SMSC LAN91C111 REV C
DATASHEET
On the transmit side for 100Mbps TX operation, data is received on the controller and then sent to the
4B5B encoder for formatting. The encoded data is then sent to the scrambler. The scrambled and
encoded data is then sent to the TP transmitter. The TP transmitter converts the encoded and
scrambled data into MLT-3 ternary format, reshapes the output, and drives the twisted pair cable.
On the receive side for 100Mbps TX operation, the twisted pair receiver receives incoming encoded
and scrambled MLT-3 data from the twisted pair cable, remove any high frequency noise, equalizes
the input signal to compensate for the effects of the cable, qualifies the data with a squelch algorithm,
and converts the data from MLT-3 coded twisted pair levels to internal digital levels. The output of the
twisted pair receiver then goes to a clock and data recovery block which recovers a clock from the
incoming data, uses the clock to latch in valid data into the device, and converts the data back to NRZ
format. The NRZ data is then unscrambled and decoded by the 4B5B decoder and descrambler,
respectively, and outputted to the Ethernet controller.
Figure 7.3 TX/10BT Frame Format
PREAMBLE SFD DA
LLC DATA
FCS SA
INTERFRAME
GAP
ETHERNET MAC
FRAME
LN
INTERFRAME
GAP
SSD PREAMBLE SFD LLC DATA FCS DA IDLE
100 BASE-TX DATA SYMBOLS
SA IDLE LN ESD
= [ 1 1 1 1...]
= [ 0 1 1 0 1 0 0 1 1 1]
= [ DATA]
= [ 1 1]
= [ 1 0 1 0 ...] 62 BITS LONG
= [ 1 1 0 0 0 1 0 0 0 1]
ESD
DA, SA, LN, LLC DATA, FCS
SSD
PREAMBLE
SFD
IDLE
BEFORE / AFTER
4B5B ENCODING,
SCRAMBLING,
AND MLT3
CODING
PREAMBLE SFD LLC DATA FCS DA IDLE
10 BASE-T DATA SYMBOLS
SA IDLE LN SOI
= [ NO TRANSITIONS]
= [ 1 1 ] WITH NO MID BIT TRANSITION
= [ DATA]
= [ 1 1]
= [ 1 0 1 0 ... ] 62 BITS LONG
SOI
DA, SA, LN, LLC DATA, FCS
SFD
PREAMBLE
IDLE
BEFORE / AFTER
MANCHESTER
ENCODING