80220 Datasheet, PDF (10/91 Pages) LSI Computer Systems – 100BASE-TX/10BASE-T Ethernet Media Interface Adapter

80220/80221
3.0 FUNCTIONAL DESCRIPTION
3.1 GENERAL
The 80220/80221 is a complete 100/10 Mbps Ethernet
Media Interface IC. The 80220/80221 has ten main
sections: controller interface, encoder, decoder, scram-
bler, descrambler, clock and data recovery, twisted pair
transmitter, twisted pair receiver, MI serial port, and
AutoNegotiation. A block diagram is shown in Figure 1.
The 80220/80221 can operate as a 100Base-TX device
(hereafter referred to as 100 Mbps mode) or as a 10Base-
T device (hereafter referred to as 10 Mbps mode). The
difference between the 100 Mbps mode and the 10 Mbps
mode is data rate, signalling protocol, and allowed wiring.
The 100 Mbps mode uses two pairs of category 5 or better
UTP or STP twisted pair cable with 4B5B encoded,
scrambled, and MLT-3 coded 62.5 MHz ternary data to
achieve a thruput of 100 Mbps. The 10 Mbps mode uses
two pairs of category 3 or better UTP or STP twisted pair
cable with Manchester encoded, 10 MHz binary data to
achieve a 10 Mbps thruput. The data symbol format on the
twisted pair cable for the 100 and 10 Mbps modes are
defined in IEEE 802.3 specifications and shown in Figure
2.
On the transmit side for 100 Mbps operation, data is
received on the controller interface from an external
Ethernet controller per the format shown in Figure 3. The
data is 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, preshapes the output, and
drives the twisted pair cable.
INTERFRAME
GAP
PREAMBLE
ETHERNET MAC FRAME
SFD
DA
SA
LN LLC DATA FCS
INTERFRAME
GAP
IDLE
IDLE
SSD
100 BASE-TX TP DATA SYMBOLS
PREAMBLE
SFD
DA
SA
LN LLC DATA FCS ESD
IDLE
IDLE = [ 1 1 1 1 ...]
SSD = [ 1 1 0 0 0 1 0 0 0 1 ]
PREAMBLE = [ 1 0 1 0 ...] 62 BITS LONG
SFD = [ 1 1 ]
DA, SA, LN, LLC DATA, FCS = [ DATA ]
ESD = [ 0 1 1 0 1 0 0 1 1 1 ]
BEFORE / AFTER
4B5B ENCODING,
SCRAMBLING, AND
MLT3 CODING
PREAMBLE
10 BASE-T TP DATA SYMBOLS
SFD
DA
SA
LN LLC DATA FCS SOI
IDLE
IDLE = [ NO TRANSITIONS ]
PREAMBLE = [ 1 0 1 0 ... ] 62 BITS LONG
SFD = [ 1 1 ]
DA, SA, LN, LLC DATA, FCS = [ DATA ]
SOI = [ 1 1 ] WITH NO MID BIT
TRANSITION
BEFORE / AFTER
MANCHESTER
ENCODING
Figure 2. Twisted Pair Frame Format
10
MD400159/E