參數(shù)資料
型號： DM9331A
文件頁數(shù)： 12/43頁
文件大?。?/td> 509K
代理商： DM9331A
DM9331
100 Mbps Twisted Pair/Fiber Ethernet Media Converter Chip
12
Preliminary
Version: DM9331-DS-P02
September 21, 2001
100Base-TX Operation
The block diagram in figure 2 provides an overview of the
functional blocks contained in the transmit section.
The transmitter section contains the following functional
blocks:
- 4B5B Encoder
- Scrambler
- Parallel to Serial Converter
- NRZ to NRZI Encoder
- NRZI to MLT-3
- MLT-3 Driver
4B5B Encoder
The 4B5B encoder converts 4-bit (4B) nibble data generated
by the MAC Reconciliation Layer into a 5-bit (5B) code group
for transmission, reference Table 1. This conversion is
required for control and packet data to be combined in code
groups. The 4B5B encoder substitutes the first 8 bits of the
MAC preamble with a J/K code-group pair (11000 10001)
upon transmit. The 4B5B encoder continues to replace
subsequent 4B preamble and data nibbles with
corresponding 5B code-groups. At the end of the transmit
packet, upon the deassertion of the Transmit Enable signal
from the MAC Reconciliation layer, the 4B5B encoder injects
the T/R code-group pair (01101 00111) indicating end of
frame. After the T/R code-group pair, the 4B5B encoder
continuously injects IDLEs into the transmit data stream until
Transmit Enable is asserted and the next transmit packet is
detected.
The DM9331 includes a Bypass 4B5B conversion option
within the 100Base-TX Transmitter for support of
applications like 100 Mbps repeaters which do not require
4B5B conversion.
Scrambler
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 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 code-group encoder via an XOR logic
function. The result is a scrambled data stream with
sufficient randomization to decrease radiated emissions at
critical frequencies.
Parallel to Serial Converter
The 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 Encoder block
NRZ to NRZI Encoder
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.
NRZI to MLT-3
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.
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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參數(shù)描述
DM9331AE 制造商:DAVICOM 制造商全稱:DAVICOM 功能描述:100 Mbps Twisted Pair/Fiber Ethernet Media Converter Chip
DM9332 制造商:DAVICOM 制造商全稱:DAVICOM 功能描述:10/100Mbps Ethernet Fiber/Twisted Pair Single Chip Media Converter
DM9332EP 制造商:DAVICOM 制造商全稱:DAVICOM 功能描述:10/100Mbps Ethernet Fiber/Twisted Pair Single Chip Media Converter
DM9334 制造商:FAIRCHILD 制造商全稱:Fairchild Semiconductor 功能描述:8-Bit Addressable Latch
DM9334 WAF 制造商:Texas Instruments 功能描述:
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