adm6996f Infineon Technologies Corporation, adm6996f Datasheet - Page 22

• Manufacturer Part Number: adm6996f
• Description: 6 Port 10/100 Mb/s Single Chip Ethernet Switch Controller
• Manufacturer: Infineon Technologies Corporation

ADM6996F
Infineon-ADMtek Co Ltd.
3.4.8 Receive Errors
3.4.9 100Base-X Link Monitor
3.4.10 Carrier Sense
3.4.11 Bad SSD Detection
The RXER signal is used to communicate receiver error conditions. While the receiver is
in a state of holding RXDV asserted, the RXER will be asserted for each code word that
does not map to a valid code-group.
The 100Base-X link monitor function allows the receiver to ensure that reliable data is
being received. Without reliable data reception, the link monitor will halt both transmit
and receive operations until such time that a valid link is detected.
The ADM6996F performs the link integrity test as outlined in IEEE 100Base-X (Clause
24) link monitor state diagram. The link status is multiplexed with 10Mbits/s link status
to form the reportable link status bit in serial management register 1h, and driven to the
LNKACT pin.
When persistent signal energy is detected on the network, the logic moves into a Link-
Ready state after approximately 500 us, and waits for an enable from the auto negotiation
module. When receive, the link-up state is entered, and the transmission and reception
logic blocks become active. Should auto negotiation be disabled, the link integrity logic
moves immediately to the link-up state after entering the link-ready state.
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.
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 ADM6996F will assert RXER and present
RXD[3:0] = 1110 to the internal MII for the cycles hat correspond to 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.
Function Description
3-4