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LXT9860/9880 — Advanced 10/100 Repeater with Integrated Management

Datasheet

Document #: 248987

Revision#: 003

Rev Date: 08/07/01

— The normal algorithm, which complies with the IEEE specification 802.3u, is available

through the management interface. This algorithm un-partitions a port only when data is

transmitted to the port for 450-560 bit times without a collision.

• Isolate. The LXT98x0 isolates any port receiving more than two successive false carrier

events. A false carrier event is a packet that does not start with a /J/K symbol pair. Note: this is

not the same function as the 100IRB isolate function, which involves isolating the backplane.

• Un-isolate. The LXT98x0 un-isolates a port that remains in the IDLE state for 33000 +/- 25%

BT or that receives a valid frame at least 450-500 BT in length.

• /T/R generation. The LXT98x0 can insert a /T/R symbol pair (End-of-Stream Delimiter) on

any incoming packet that does not include one. This feature is optional, and is enabled through

the management interface.

• Jabber. The LXT98x0 ignores any receiver remaining active for more than 57,500 bit times.

The LXT98x0 exits this state when either one of the following conditions is met:

— On power-up reset

— When carrier is no longer detected

Note:

The Isolate, Partition, and Symbol Error functions do not apply to MII ports.

3.4.2

10 Mbps Repeater Operation

The LXT98x0 contains a complete 10 Mbps Repeater State Machine (10RSM) that is fully IEEE

802.3 compliant. Any port configured for 10 Mbps operation is automatically connected to the

10 Mbps Repeater. This includes any of the media and MII ports configured for 10 Mbps operation.

The 10RSM has its own Inter-Repeater Backplane (10IRB). Multiple LXT98x0s can be cascaded

on the 10IRB and operate as one repeater segment. Data from any port is forwarded to all other

ports in the cascade.

The LXT98x0 maintains a complete set of statistics on its 10 Mbps repeater segment. These are

accessible through the high-speed serial management interface.

The LXT98x0 performs the following 10 Mbps repeater functions:

• Signal amplification, wave-shape restoration, and data-frame forwarding.

• Preamble regeneration. All outgoing packets have a minimum 56-bit preamble and 8-bit SFD.

• SOP, SOJ, EOP, EOJ delays meet IEEE 802.3 section 9.5.5 and 9.5.6 requirements.

• Collision Enforcement. During a 10 Mbps collision, the LXT98x0 drives a jam signal

(“1010”) to all ports for a minimum of 96 bit times until the collision ends.

• Partition. The LXT98x0 partitions any port in excess of 31 consecutive collisions. Once

partitioned, the LXT98x0 continues monitoring and transmitting to the port, but does not

repeat data received from the port until it properly un-partitions. (Also partitions for excessive

length of a collision.)

• Un-partition. The algorithm, which complies with the IEEE 802.3 specification, un-partitions

a port when data can be either received or transmitted from the port for 450-560 bit times

without a collision on that port.

• Jabber. The LXT98x0 asserts a minimum-IFG idle period when a port transmits for longer

than 40,000 to 75,000 bit times.

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