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LXT9883/9863 — Advanced 10/100 Unmanaged Repeater

Datasheet

Document #: 249115

Revision #: 003

Rev. Date: 08/07/01

3.2.2

Link Establishment and Port Connection

Once a port establishes link, the LXT98x3 automatically connects it to the appropriate repeater

state machine. If link loss is detected and auto-negotiation is enabled, the port returns to the auto-

negotiation state.

3.3

Interface Descriptions

The LXT9883 and LXT9863 provide eight and six network interface ports, respectively. Each port

is a twisted-pair interface that directly supports 100BASE-TX (100TX) and 10BASE-T (10T)

Ethernet applications and fully complies with IEEE 802.3 standards. A common termination circuit

is used.

3.3.1

Twisted-Pair Interface

The LXT98x3 pinout is optimized for dual-height RJ-45 connectors. The twisted-pair interface for

each port consists of two differential signal pairs — one for transmit and one for receive. The

transmit signal pair is TPOP/TPON, the receive signal pair is TPIP/TPIN.

The transmitter requires magnetics with 1:1 turns ratio. The center tap of the primary side of the

transmit winding must be tied to a quiet VCC for proper operation.

The receiver requires magnetics with a 1:1 turns ratio, and a load of 100

Ω. When the twisted-pair

port is enabled, the receiver actively biases its inputs to approximately 2.8V. A 4 k

Ω load is always

present across the TPIP/TPIN pair.

When used in 100TX applications, the LXT98x3 sends and receives a continuous, scrambled

125 Mbps MLT-3 waveform on this interface. In the absence of data, IDLE symbols are sent and

received in order to maintain the link.

When used in 10T applications, the LXT98x3 sends and receives a non-continuous, 10 Mbps

Manchester-encoded waveform. To maintain link during idle periods, the LXT98x3 sends link

pulses every 16 ms, and expects to receive them every 10 to 20 ms. Each 10T port automatically

detects and sends link pulses, and disables its transmitter if link pulses are not detected. Each

10BASE-T port can detect and automatically correct for polarity reversal on the TPIP/N inputs.

The 10BASE-T interface provides integrated filters using Intel’s patented filter technology. These

filters facilitate low-cost stack designs to meet EMI requirements.

3.3.2

Media Independent Interface

The LXT98x3 has two identical MII interfaces. The MII has been designed to allow expansion to a

Media Access Controller (MAC) as shown in Figure 4. This interface is not MDIO/MDC capable.

These MII ports can be set via hardware tie ups/downs to be either 10 Mbps or 100 Mbps. These

ports are not the full MII drive strength and are intended only for point-to-point links.

9883 Datasheet(PDF) 18 Page - Intel Corporation

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