Datasheet

DP83849IF

www.ti.com

SNOSAX8D –JUNE 2009–REVISED APRIL 2013

7.3 100BASE-FX OPERATION

The DP83849IF provides IEEE 802.3 compliant 100BASE-FX operation. Configuration of FX mode is via

strap option, or through the register interface.

7.3.1 100BASE-FX Transmit

In 100BASE-FX mode, the device Transmit Pins connect to an industry standard Fiber Transceiver with

PECL signalling through a capacitively coupled circuit.

In FX mode, the device bypasses the Scrambler and the MLT3 encoder. This allows for the transmission

of serialized 5B4B encoded NRZI data at 125 MHz.

The only added functionality from 100BASE-TX is the support for Far-End Fault data generation.

7.3.2 100BASE-FX Receive

In 100BASE-FX mode, the device Receive pins connect to an industry standard Fiber Transceiver with

PECL signalling through a capacitively coupled circuit.

In FX mode, the device bypasses MLT3 Decoder and the Descrambler. This allows for the reception of

serialized 5B4B encoded NRZI data at 125 MHz.

The only added functionality for 100BASE-FX from 100BASE-TX is the support of Far-End Fault detection.

7.3.3 Far-End Fault

Since 100BASE-FX does not support Auto-Negotiation, a Far-End Fault facility is included which allows for

detection of link failures.

When no signal is being received as determined by the Signal Detect function, the device sends a Far-

End Fault indication to the far-end peer. The Far-End Fault indication is comprised of 3 or more repeating

cycles, each consisting of 84 one’s followed by 1 zero. The pattern is such that it will not satisfy the

100BASE-X carrier sense mechanism, but is easily detected as the Fault indication. The pattern will be

transparent to devices that do not support Far-End Fault.

The Far-End Fault detection process continuously monitors the receive data stream for the Far-End Fault

indication. When detected, the Link Monitor is forced to deassert Link status. This causes the device to

transmit IDLE’s on its transmit path.

7.4 10BASE-T TRANSCEIVER MODULE

The 10BASE-T Transceiver Module is IEEE 802.3 compliant. It includes the receiver, transmitter, collision,

heartbeat, loopback, jabber, and link integrity functions, as defined in the standard. An external filter is not

required on the 10BASE-T interface since this is integrated inside the DP83849IF. This section focuses on

the general 10BASE-T system level operation.

7.4.1 Operational Modes

The DP83849IF has two basic 10BASE-T operational modes:

• Half Duplex mode

• Full Duplex mode

7.4.1.1 Half Duplex Mode

In Half Duplex mode the DP83849IF functions as a standard IEEE 802.3 10BASE-T transceiver

supporting the CSMA/CD protocol.

Submit Documentation Feedback

Product Folder Links: DP83849IF