adm6999ux Infineon Technologies Corporation, adm6999ux Datasheet - Page 20

• Manufacturer Part Number: adm6999ux
• Description: Adm6999u 9 Port 10/100 Mb/s Single Chip Ethernet Switch Controller
• Manufacturer: Infineon Technologies Corporation

3.2.2.10
Carrier sense (CRS) for 100Mbits/s operation is asserted upon the detection of two noncontiguous zeros occurring
within any 10-bit boundary of the received data stream.
The carrier sense function is independent of symbol alignment. In switch mode, CRS is asserted during either
packet transmission or reception. For repeater mode, CRS is asserted only during packet reception. When the idle
symbol pair is detected in the received data stream, CRS is de-asserted. In repeater mode, CRS is only asserted
due to receive activity. CRS is intended to encapsulate RXDV.
3.2.2.11
A bad start of stream delimiter (Bad SSD) is an error condition that occurs in the 100Base-X receiver if carrier is
detected (CRS asserted) and a valid /J/K set of code-group (SSD) is not received.
If this condition is detected, then the ADM6999U/UX will assert RXER and present RXD[3:0] = 1110 to the internal
MII for the cycles hat corresponding to the received 5B code-groups until at least two idle code-groups are
detected. Once at least two idle code groups are detected, RXER and CRS become de-asserted.
3.2.2.12
Auto negotiation provides a mechanism for transferring information from the Local Station to the link Partner that
a remote fault has occurred for 100Base-TX. As auto negotiation is not currently specified for operation over fiber,
the far end fault indication function (FEFI) provides this capability for 100Base-FX applications.
A remote fault is an error in the link that one station can detect while the other cannot. An example of this is a
disconnected wire at a station’s transmitter. This station will be receiving valid data and detect that the link is good
via the link integrity monitor, but will not be able to detect that its transmission is not propagating to the other
station.
A 100Base-FX station that detects such a remote fault may modify its transmitted idle stream from all ones to a
group of 84 ones followed by a single 0. This is referred to as the FEFI idle pattern.
3.2.3
ADM6999U/UX implements a TP-PMD compliant transceiver for 100Base-TX operation. The differential
transmitting driver is shared by the 10Base-T and 100Base-TX subsystems. This arrangement results in one
device that uses the same external magnetic for both the 10Base-T and the 100Base-TX transmission with simple
RC component connections. The individually wave-shaped 10Base-T and 100Base-TX transmitting signals are
multiplexed in the transmission output driver selection.
3.2.3.1
The ADM6999U/UX 100Base-TX transmission driver implements MLT-3 translation and wave-shaping functions.
The rise/fall time of the output signal is closely controlled to conform to the target range specified in the ANSI TP-
PMD standard.
3.2.3.2
For 100Base-TX operation, the incoming signal is detected by the on-chip twisted-pair receiver that consists of a
differential line receiver, an adaptive equalizer and a base-line wander compensation circuits.
The ADM6999U/UX uses an adaptive equalizer that changes filter frequency response in accordance with cable
length. The cable length is estimated based on the incoming signal strength. The equalizer tunes itself
automatically for any cable length to compensate for the amplitude and phase distortions incurred from the cable.
Data Sheet
Carrier Sense
Bad SSD Detection
Far-End Fault
100Base-TX Transceiver
Transmit Drivers
Twisted-Pair Receiver
20
Rev. 1.42, 2005-11-25
ADM6999U/UX
Data Sheet
Descriptions