SMSC LAN91C111 - Manual (Page 28)

10/100 Non-PCI Ethernet Single Chip MAC + PHY
Datasheet
Revision 1.91 (08-18-08) 28 SMSC LAN91C111 REV C
DATASHEET
* These 5B codes are not used. For decoder, these 5B codes are decoded to 4B 0000. For encoder,
4B 0000 is encoded to 5B 11110, as shown in symbol Data 0.
The 4B5B decoder detects SSD, ESD and codeword errors in the incoming data stream as specified
in IEEE 802.3. These errors are indicated by asserting RX_ER output while the errors are being
transmitted across RXD[3:0], and they are also indicated in the serial port by setting SSD, ESD, and
codeword error bits in the PHY MI serial port Status Output register.
Manchester Decoder - 10 Mbps
In Manchester coded data, the first half of the data bit contains the complement of the data, and the
second half of the data bit contains the true data. The Manchester decoder in the LAN91C111 converts
the Manchester encoded data stream from the TP receiver into NRZ data for the controller interface
by decoding the data and stripping off the SOI pulse. Since the clock and data recovery block has
already separated the clock and data from the TP receiver, the Manchester decoding process to NRZ
data is inherently performed by that block.
3 Data 3 10101 0011
4 Data 4 01010 0100
5 Data 5 01011 0101
6 Data 6 01110 0110
7 Data 7 01111 0111
8 Data 8 10010 1000
9 Data 9 10011 1001
A Data A 10110 1010
B Data B 10111 1011
C Data C 11010 1100
D Data D 11011 1101
E Data E 11100 1110
F Data F 11101 1111
I Idle 11111 0000
J SSD #1 11000 0101
K SSD #2 10001 0101
T ESD #1 01101 0000
R ESD #2 00111 0000
H Halt 00100 Undefined
--- Invalid codes All others* 0000*
Table 7.1 4B/5B Symbol Mapping (continued)
SYMBOL NAME DESCRIPTION 5B CODE 4B CODE