SMSC LAN8710i User Manual

MII/RMII 10/100 Ethernet Transceiver with HP Auto-MDIX and flexPWR

® 

 Technology in a Small Footprint

Revision 1.0 (04-15-09)

20

SMSC LAN8710/LAN8710i

The transmit data passes from the MII 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 

. 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.

The encoding process may be bypassed by clearing bit 6 of register 31. When the encoding is
bypassed the 5

th

 transmit data bit is equivalent to TXER. 

Note that encoding can be bypassed only when the MAC interface is configured to operate in MII
mode.

11110

0

0

0000 DATA

0

0000 DATA

01001

1

1

0001

1

0001

10100

2

2

0010

2

0010

10101

3

3

0011

3

0011

01010

4

4

0100

4

0100

01011

5

5

0101

5

0101

01110

6

6 0110

6

0110

01111

7

7 0111

7

0111

10010

8

8 1000

8

1000

10011

9

9 1001

9

1001

10110

A

A 1010

A

1010

10111

B

B 1011

B

1011

11010

C

C 1100

C

1100

11011

D

D 1101

D

1101

11100

E

E 1110

E

1110

11101

F

F 1111

F

1111

11111

I

IDLE

Sent after /T/R until TXEN

11000

J

First nibble of SSD, translated to “0101” 
following IDLE, else RXER 

Sent for rising TXEN

10001

K

Second nibble of SSD, translated to 
“0101” following J, else RXER

Sent for rising TXEN

01101

T

First nibble of ESD, causes de-assertion 
of CRS if followed by /R/, else assertion 
of RXER

Sent for falling TXEN