AC208-DS03-R datasheet(13/58 Pages) BOARDCOM

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Preliminary Data Sheet

AC208

07/08/02

B roa dcom

Document

AC208-DS04-405-R

Auto-Negotiation and Miscellaneous Functions

Page 5

AUTO-NEGOTIATION AND MISCELLANEOUS FUNCTIONS

Each of the transceivers contain the ability to negotiate its mode of operation over the twisted pair using the auto-negotiation

mechanism defined in the clause 28 IEEE 802.3u specification. Auto-negotiation may be disabled by software via EEPROM.

The transceiver automatically chooses its mode of operation by detecting the incoming signal.

During auto-negotiation, the auto-negotiation advertisement register is sent to its link partner through a series of fast link

pulse (FLP). When auto-negotiation enabled, Transceiver sends FLP during the following conditions:

•

Power on

•

Link loss

•

Restart command

At the same time, the device monitors incoming data to determine its mode of operation. Parallel detection circuit is enabled

as soon as 10BASE-T idle or 100BASE-TX idle is detected. The mode of operation is configured based on the technology

of the incoming signal. When the device receives a burst of FLP from its link partner with three identical link code words

(ignoring acknowledge bit), it stores these code words in the auto-negotiation link partner ability register and waits for the

next three identical code words. Once the device detects the second code word, it configures itself to the highest technology

that is common to both ends. The technology priorities are:

100BASE-TX, half-duplex

10BASE-T half-duplex

Once auto-negotiation is complete, the status register reflects the actual speed that was chosen.

PARALLEL DETECTION

The Transceiver also checks for 10BASE-T NLP or 100BASE-TX idle symbols. If either is detected, the device automatically

configures to match the detected operating speed in half-duplex mode. This ability allows the device to communicate with

legacy 10BASE-T and 100BASE-TX systems.

CARRIER SENSE/RXDV FOR MII PORT ONLY

Carrier sense is asserted asynchronously on the CRS pins as soon as activity is detected on the receive data stream.

RX_DV is asserted as soon as a valid SSD (Start-of-Stream Delimiter) is detected. Carrier sense and RX_DV are de-

asserted synchronously upon detection of a valid end of stream delimiter or two consecutive idle code groups in the receive

data stream. If carrier sense is asserted and a valid SSD is not detected immediately, RX_ER is asserted instead of RX_DV.

In 10BASE-T mode, carrier sense is asserted asynchronously on the CRS pin when valid preamble activity is detected on

the RXIP/RXIN pins. In half-duplex mode, the CRS is activated during transmit and receive of data.

CABLE LENGTH MONITOR

The AC208 can also detect the length of the cable and display the result in the interrupt control/status register (such as, 0000

stands for less than 10m cable used, 0001 stands for ~ 10m of cable, and 1111 stands for 150m cable).

AC208-DS03-R 数据表(PDF) 13 Page - Broadcom Corporation.

AC208-DS03-R 数据表(HTML) 13 Page - Broadcom Corporation.

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