®
Small Footprint MII/RMII 10/100 Ethernet Transceiver with HP Auto-MDIX and flexPWR Technology
Datasheet
For RMII, the MAC controller drives the transmit data onto the TXD bus and asserts TXEN to indicate
valid data. The data is latched by the transceiver’s RMII block on the rising edge of REF_CLK. The
data is in the form of 2-bit wide 50MHz data.
3.1.1.2
4B/5B Encoding
The transmit data passes from the MII/RMII block to the 4B/5B encoder. This block encodes the data
from 4-bit nibbles to 5-bit symbols (known as “code-groups”) according to Table 3.1. Each 4-bit data-
nibble is mapped to 16 of the 32 possible code-groups. The remaining 16 code-groups are either used
for control information or are not valid.
The first 16 code-groups are referred to by the hexadecimal values of their corresponding data nibbles,
0 through F. The remaining code-groups are given letter designations with slashes on either side. For
example, an IDLE code-group is /I/, a transmit error code-group is /H/, etc.
Table 3.1 4B/5B Code Table
CODE
GROUP
RECEIVER
INTERPRETATION
TRANSMITTER
INTERPRETATION
SYM
11110
01001
10100
10101
01010
01011
01110
01111
10010
10011
10110
10111
11010
11011
11100
11101
11111
11000
0
1
2
3
4
5
6
7
8
9
A
B
C
D
E
F
I
0
1
2
3
4
5
6
7
8
9
A
B
C
D
E
F
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
DATA
0
1
2
3
4
5
6
7
8
9
A
B
C
D
E
F
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
DATA
IDLE
Sent after /T/R until TXEN
Sent for rising TXEN
J
First nibble of SSD, translated to “0101”
following IDLE, else RXER
10001
01101
K
T
Second nibble of SSD, translated to
“0101” following J, else RXER
Sent for rising TXEN
Sent for falling TXEN
First nibble of ESD, causes de-assertion
of CRS if followed by /R/, else assertion
of RXER
Revision 1.4 (08-23-12)
20
SMSC LAN8710A/LAN8710Ai
DATASHEET
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