SMSC flexpwr lan8710 User Manual

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

® 

 Technology in a Small Footprint

SMSC LAN8710/LAN8710i

21

Revision 1.0 (04-15-09)

Repeated data patterns (especially the IDLE code-group) can have power spectral densities with large
narrow-band peaks. Scrambling the data helps eliminate these peaks and spread the signal power
more uniformly over the entire channel bandwidth. This uniform spectral density is required by FCC
regulations to prevent excessive EMI from being radiated by the physical wiring.

The seed for the scrambler is generated from the transceiver address, PHYAD[4:0], ensuring that in
multiple-transceiver applications, such as repeaters or switches, each transceiver will have its own
scrambler sequence.

The scrambler also performs the Parallel In Serial Out conversion (PISO) of the data.

The scrambler block passes the 5-bit wide parallel data to the NRZI converter where it becomes a
serial 125MHz NRZI data stream. The NRZI is encoded to MLT-3. MLT3 is a tri-level code where a
change in the logic level represents a code bit “1” and the logic output remaining at the same level
represents a code bit “0”.

The MLT3 data is then passed to the analog transmitter, which drives the differential MLT-3 signal, on
outputs TXP and TXN, to the twisted pair media across a 1:1 ratio isolation transformer. The 10Base-
T and 100Base-TX signals pass through the same transformer so that common “magnetics” can be
used for both. The transmitter drives into the 100

Ω impedance of the CAT-5 cable. Cable termination

and impedance matching require external components.

00111

R

Second nibble of ESD, causes 
deassertion of CRS if following /T/, else 
assertion of RXER

Sent for falling TXEN

00100

H

Transmit Error Symbol

Sent for rising TXER

00110

V

INVALID, RXER if during RXDV

INVALID

11001

V

INVALID, RXER if during RXDV

INVALID

00000

V

INVALID, RXER if during RXDV

INVALID

00001

V

INVALID, RXER if during RXDV

INVALID

00010

V

INVALID, RXER if during RXDV

INVALID

00011

V

INVALID, RXER if during RXDV

INVALID

00101

V

INVALID, RXER if during RXDV

INVALID

01000

V

INVALID, RXER if during RXDV

INVALID

01100

V

INVALID, RXER if during RXDV

INVALID

10000

V

INVALID, RXER if during RXDV

INVALID