5222-DS01-R datasheet(13/76 Pages) BOARDCOM

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Preliminary Data Sheet

BCM5222

7/20/04

Broadcom Corporation

Document 5222-DS02-405-R

Functional Description

Page 1

Section 1: Functional Description

OVERVIEW

The BCM5222 is a dual-port, single-chip Fast Ethernet transceiver. It performs all of the physical layer interface functions

for 100BASE-TX full-or half-duplex Ethernet on CAT 5 twisted pair cable and 10BASE-T full-or half-duplex Ethernet on CAT

3, 4, or 5 cable.

The chip performs 4B5B, MLT3, NRZI, and Manchester encoding and decoding, clock and data recovery, stream cipher

scrambling/descrambling, digital adaptive equalization, line transmission, carrier sense and link integrity monitor, auto-

negotiation and Media Independent Interface (MII) management functions. Each of the two PHYs in the BCM5222 can be

connected to a MAC switch controller through the MII on one side, and can connect directly to the network media on the

other side (through isolation transformers for unshielded twisted pair (UTP)). The BCM5222 is fully compliant with the IEEE

802.3 and 802.3u standards.

ENCODER/DECODER

In 100BASE-TX mode, the BCM5222 transmits and receives a continuous data stream on twisted-pair cable. When the MII

transmit enable is asserted, nibble-wide (4-bit) data from the transmit data pins is encoded into 5-bit code groups and

inserted into the transmit data stream. The 4B5B encoding is shown in Table 1 on page 4. The transmit packet is

encapsulated by replacing the first 2 nibbles of preamble with a start of stream delimiter (J/K codes) and appending an end

of stream delimiter (T/R codes) to the end of the packet. When the MII transmit error input is asserted during a packet, the

transmit error code group (H) is sent in place of the corresponding data code group. The transmitter repeatedly sends the

idle code group between packets.

In 100BASE-TX mode, the encoded data stream is scrambled by a stream cipher block and then serialized and encoded

into MLT3 signal levels. A multi-mode transmit DAC is used to drive the MLT3 data onto the twisted pair cable.

Following baseline wander correction, adaptive equalization, and clock recovery in 100BASE-TX mode, the receive data

stream is converted from MLT3 to serial NRZ data. The NRZ data is descrambled by the stream cipher block and then

deserialized and aligned into 5-bit code groups.

The 5-bit code groups are decoded into 4-bit data nibbles, as shown in Table 1. The start of stream delimiter is replaced with

preamble nibbles and the end of stream delimiter and idle codes are replaced with all zeros. The decoded data is driven onto

the MII receive data pins. When an invalid code group is detected in the data stream, the BCM5222 asserts the MII RXER

signal. The chip also asserts RXER for several other error conditions that improperly terminate the data stream. While RXER

is asserted, the receive data pins are driven with a 4-bit code indicating the type of error detected. The error codes are listed

in Table 2 on page 5.

In 10BASE-T mode, Manchester encoding and decoding is performed on the data stream. The multimode transmit DAC

performs pre-equalization for 100 meters of CAT 3 cable.

5222-DS01-R 数据表(PDF) 13 Page - Broadcom Corporation.

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