DM8603EP DAVICOM [Davicom Semiconductor, Inc.], DM8603EP Datasheet - Page 88

• Manufacturer Part Number: DM8603EP
• Description: 10/100 Mbps 3-port Ethernet Switch Controller with MII / RMII Interface
• Manufacturer: DAVICOM [Davicom Semiconductor, Inc.]

9.4 Internal PHY Functions
9.4.1
9.4.1.1
(5B) code group for transmission, see 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
desertions of the Transmit Enable signal from the MAC Reconciliation layer, the 4B5B encoder injects the
T/R code-group pair (01101 00111) indicating the 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.
9.4.1.2
across the frequency spectrum at the media connector and on the twisted pair cable in 100Base-TX
operation.
frequency range. Without the scrambler, energy levels on the cable could peak beyond FCC limitations at
frequencies related to the repeated 5B sequences, like the 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.
9.4.1.3
(converts it from a parallel to a serial data stream). The serialized data stream is then presented to the NRZ
to NRZI encoder block
9.4.1.4
compatibility with the TP-PMD standard, for 100Base -TX transmission over Category-5 unshielded twisted
pair cable.
9.4.1.5
Preliminary datasheet
DM8603-12-DS-P01
November 8, 2010
The transmitter section contains the following functional blocks:
The 4B5B encoder converts 4-bit (4B) nibble data generated by the MAC Reconciliation Layer into a 5-bit
The scrambler is required to control the radiated emissions (EMI) by spreading the transmit energy
By scrambling the data, the total energy presented to the cable is randomly distributed over a wide
The Parallel to Serial Converter receives parallel 5B scrambled data from the scrambler, and serializes it
After the transmit data stream has been scrambled and serialized, the data must be NRZI encoded for
The MLT-3 conversion is accomplished by converting The data stream output, from the NRZI encoder
100Base-TX Operation
4B5B Encoder
Scrambler
Parallel to Serial Converter
NRZ to NRZI Converter
NRZI to MLT-3
MLT-3 Driver
4B5B Encoder
Scrambler
Parallel to Serial Converter
NRZ to NRZI Encoder
MLT-3 Converter
10/100 Mbps 3-port Ethernet Switch Controller with MII / RMII Interface
DM8603
88