DM9301F datasheet(11/22 Pages) ETC

11 / 22 page

DM9301

100Mbps Ethernet Fiber/Twisted Pair Single Chip Media Converter

Final

Version: DM9301-DS-F02

May 8, 2000

FX Serial to Parallel Converter

The Serial to Parallel converter receives a serial

data stream from the NRZI to NRZ converter, and

converts the data stream to parallel data to be

presented to the scrambler. The parallel data format

presented to the TX scrambler is 5B coded.

FX Code Group Alignment Monitor

The FX Code Group Alignment block receives non-

aligned 5B data from the FX Serial to Parallel

converter and monitors it for 5B code group

violations. FX Code Group Alignment occurs after

the J/K is detected, and subsequent data is

monitored on a fixed boundary. If a violation is

detected, the FX Code Group Alignment Monitor

block signals the error to the Link Status Monitor

block. In turn, the Link Status Monitor block flashes

the FX error LED (FXERRLED#).

TX Scrambler

The scrambler also receives data from the FX Serial

to Parallel converter. Data from the serial to parallel

conversion block is 5B symbol encoded. The

scrambler is required to control the radiated

emissions (EMI) by spreading the transmit energy

across the frequency spectrum at the media

connector and on the twisted pair cable in 100Base-

TX transmit operation.

By scrambling the data, the total energy presented

to the cable is randomly distributed over a wide

frequency range. Without the scrambler, energy

levels on the cable could peak beyond FCC

limitations at frequencies related to repeated 5B

sequences like continuous transmission of IDLE

symbols. The scrambler output is combined with the

NRZ 5B data from the FX Serial to Parallel

converter via an XOR logic function. The result is a

scrambled data stream with sufficient randomization

to decrease radiated emissions at critical

frequencies.

TX Parallel to Serial Converter

The TX Parallel to Serial converter receives parallel

5B scrambled data from the scrambler and

serializes it (converts it from a parallel to a serial

data stream). The serialized data stream is then

presented to the NRZ to NRZI converter block

TX NRZ to NRZI Converter

After the transmit data stream has been scrambled

and serialized, the data must be NRZI encoded for

compatibility with the TP-PMD standard for

100Base-TX transmission over Category-5

unshielded twisted pair cable.

TX MLT-3 Converter

The MLT-3 conversion is accomplished by

converting the data stream output from the NRZI

encoder into two binary data streams with

alternately phased logic one events.

TX MLT-3 Driver

The two binary data streams created at the MLT-3

converter are fed to the twisted pair output driver

which converts these streams to current sources

and alternately drives either side of the transmit

transformer primary winding resulting in a minimal

current MLT-3 signal.

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