AC207-DS02-R datasheet(15/60 Pages) BOARDCOM

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Preliminary Data Sheet

AC207

07/08/02

B roa dcom

Document

AC207-DS04-405-R

Cable Length Monitor

Page 5

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-assert-

ed 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 AC207 can also detect the length of the cable and display the result in the interrupt control/status register, i.e., 0000

stands for < 10m cable used, 0001 stands for ~ 10 meter of cable, 1111 stands for 150 meter cable. It detects the proper

connectivity of the cable and helps to manage the cable distribution.

BRIDGE FUNCTION

MII INTERFACE

The bridge supports MII for 10/100 Mbps. Port 0 of the bridge can support either 10 or 100, while port 1 supports only at 100

Mbps. Refer to the mode pin table to configure port 0.

FORWARDING SCHEME

The bridge supports the store-and-forward scheme only. It does not support cut-through-forward. With store-and-forward,

the incoming packet should be completely received to the buffer without error before it can be sent out.

ADDRESS RECOGNITION

The self-learning bridge function is based on source address field of packets. The bridge uses the XOR hashing algorithm

to address look-up table. Programmable aging time and fast aging control is supported.

RESET AND RESTART

At the power-on, the bridge initially goes to SRAM self-test mode. It generates 8 patterns to evaluate SRAM status.

MEDIA ACCESS CONTROL

The Bridge MAC compiles with certain IEEE 802.3 MAC protocols such as frame formatting and collision handling but does

generate CRC codes. It generates a 56-bit preamble and start of frame delimiter while a packet is sending. In half-duplex

mode, the device listens before transmitting, to prevent traffic jam. During collision, a packet is retransmitted at a random

time.

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