5220-DS01-R datasheet(17/90 Pages) BOARDCOM

17 / 90 page

Preliminary Data Sheet

BCM5220

04/20/04

Broa d c om Co rp o r a t i o n

Document

5220-DS04-405-R

Far-End Fault

Page 5

FAR-END FAULT

Auto-negotiation provides a remote fault capability for detection of asymmetric link failures. Since auto-negotiation is not

available for 100BASE-FX, the BCM5220 implements the IEEE 802.3 standard Far-End Fault mechanism for the indication

and detection of remote error conditions. When the Far-End Fault mechanism is enabled, a transceiver transmits the Far-

End Fault Indication whenever a receive channel failure is detected (signal detect is deasserted). The transceiver also

continuously monitors the receive channel when a valid signal is present (signal detect asserted). When its link partner is

indicating a remote error, the transceiver forces its link monitor into the link fail state and sets the remote fault bit in the MII

status register.

The Far-End Fault mechanism is enabled by default in 100BASE-FX mode and disabled in 100BASE-TX and 10BASE-T

modes, and can be controlled by software after reset.

MII MANAGEMENT

The BCM5220 contains a complete set of MII management registers accessible by using the management clock line (MDC)

and the bidirectional serial data line (MDIO). Many transceivers can be bussed together on a single MDIO/MDC wire pair by

giving each a unique PHY address, defined by configuring the five external PHY address input pins.

Every time an MII read or write operation is executed, the BCM5220 compares the operation’s PHY address with its own

PHY address definition. The operation is executed only when the addresses match.

For further details, see Section 5: “Register Summary” on page 18.

Table 1: 4B5B Encoding

Name

4B code

5B Code

Meaning

0000

11110

Data 0

0001

01001

Data 1

0010

10100

Data 2

0011

10101

Data 3

0100

01010

Data 4

0101

01011

Data 5

0110

01110

Data 6

0111

01111

Data 7

1000

10010

Data 8

1001

10011

Data 9

1010

10110

Data A

1011

10111

Data B

1100

11010

Data C

1101

11011

Data D

1110

11100

Data E

1111

11101

Data F

0000*

11111

Idle

0101*

11000

Start-of-Stream Delimiter, Part 1

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