5238-DS03-405-R datasheet(10/76 Pages) BOARDCOM

10 / 76 page

BCM5238

Advance Data Sheet

1/31/03

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

Page 2

Link Monitor

Document

5238-DS03-405-R

LINK MONITOR

In 100BASE-TX mode, receive signal energy is detected by monitoring the receive pair for transitions in the signal level.

Signal levels are qualified using squelch detect circuits. When no signal or certain invalid signals are detected on the receive

pair, the link monitor enters and remains in the Link Fail state where only idle codes are transmitted. When a valid signal is

detected on the receive pair for a minimum period of time, the link monitor enters the Link Pass state and the transmit and

receive functions are enabled.

In 10BASE-T mode, a link-pulse detection circuit constantly monitors the RD± pins for the presence of valid link pulses.

CARRIER SENSE

In DTE mode, the carrier sense and receive data valid signals are multiplexed on the same pin. The carrier sense is asserted

asynchronously on CRS_DV as soon as valid activity is detected in the receive data stream. Loss of carrier shall result in

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

0000a

11111

Idle

0101a

11000

Start-of-stream delimiter, part 1

0101a

10001

Start-of-stream delimiter, part 2

0000a

01101

End-of-stream delimiter, part 1

0000a

00111

End-of-stream delimiter, part 2

1000

00100

Transmit error (used to force signalling errors)

0111

00000

Invalid Code

0111

00001

Invalid Code

0111

00010

Invalid Code

0111

00011

Invalid Code

0111

00101

Invalid Code

0111

00110

Invalid Code

0111

01000

Invalid Code

0111

01100

Invalid Code

0111

10000

Invalid Code

0111

11001

Invalid Code

a. Treated as invalid code (mapped to 0111) when received in data field.

Table 1: 4B5B encoding (Cont.)

Name

4B Code

5B Code

Meaning

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