lxt9763 Intel Corporation, lxt9763 Datasheet - Page 33

• Manufacturer Part Number: lxt9763
• Description: Fast Ethernet 10/100 Hex Transceiver With Full Mii
• Manufacturer: Intel Corporation

1.10.2.4
1.11
Datasheet
The scrambler/descrambler can be bypassed by setting bit 16.12 = 1. The scrambler is
automatically bypassed when the fiber port is enabled. Scramber bypass is provided for diagnostic
and test support.
Baseline Wander Correction (100TX Only)
The LXT9763 provides a baseline wander correction function, making the device robust under all
network operating conditions. The MLT3 coding scheme used in 100BASE-TX is by definition
“unbalanced”. This means that the DC average value of the signal voltage can “wander”
significantly over short time intervals (tenths of seconds). This wander can cause receiver errors,
particularly in less robust designs, at long line lengths (100 meters). The exact characteristics of the
wander are completely data dependent.
The LXT9763 baseline wander correction characteristics allow the device to recover error-free data
while receiving worst-case “killer” packets over all cable lengths.
Polarity Correction
The LXT9763 automatically detects and corrects for the condition where the receive signal (TPIP/
N) is inverted. Reversed polarity is detected if eight inverted link pulses, or four inverted end-of-
frame (EOF) markers, are received consecutively. If link pulses or data are not received by the
maximum receive time-out period, the polarity state is reset to a non-inverted state.
Fiber PMD Sublayer
The LXT9763 provides a PECL interface for connection to an external fiber-optic transceiver.
(The external transceiver provides the PMD function for fiber media.) The LXT9763 uses an
NRZI format for the fiber interface.
The fiber interface operates at 100 Mbps and does not support 10FL applications.
Far End Fault Indications
The LXT9763 does not provide Signal Detect pins and therefore does not independently detect
signal faults. However, the device can detect a far end fault code embedded in the received data
stream and uses bit 1.4 to report far end fault indications received from its link partner. Bit 1.4 is set
once and clears when read.
A far end fault condition causes the LXT9763 to drop the link unless Forced Link Pass is selected
(16.14 = 1). Link down condition is then reported via interrupts and status bits.
10 Mbps Operation
The LXT9763 can operate as a standard 10BASE-T transceiver, supporting all the standard 10
Mbps functions. During 10BASE-T (10T) operation, the LXT9763 transmits and receives
Manchester-encoded data across the network link. When the MAC is not actively transmitting data,
the LXT9763 drives link pulses onto the line.
In 10T mode, the polynomial scrambler/descrambler is inactive. Manchester-encoded signals
received from the network are decoded by the LXT9763 and sent across the MII to the MAC. The
10M reversed polarity correction function is the same as the 100M function described on page 33.
Fast Ethernet 10/100 Hex Transceiver with Full MII — LXT9763
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