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Cortina Systems LXT9785 and LXT9785E Advanced 8-Port 10/100 Mbps PHY Transceivers
LXT9785/LXT9785E
Datasheet
249241, Revision 11.0
16 April 2007
4.2 Interface Descriptions
4.2.1.1
Twisted-Pair Interface
The LXT9785/LXT9785E supports either 100BASE-TX or 10BASE-T connections over
100
Ω, Category 5, Unshielded Twisted-Pair (UTP). Only a transformer, RJ-45, and
bypass capacitors are required to complete this interface. Using waveshaping technology,
the transmitter shapes the outgoing signal to help reduce the need for external EMI filters.
page 43) allow the designer to match the output waveform to the magnetic characteristics.
Both transmit and receive terminations are built into the LXT9785/LXT9785E so no
external components are required between the LXT9785/LXT9785E and the external
transformer. The transmitter uses a transformer with a center tap to help reduce power
consumption.
When operating at 100 Mbps, MLT3 symbols are continuously transmitted and received.
When not transmitting data, the LXT9785/LXT9785E generates “IDLE” symbols.
During 10 Mbps operation, LXT9785/LXT9785E encoded data is exchanged. When no
data are being exchanged, the line is left in an idle state with NLPs transmitted to maintain
link.
Figure 7
Interface Signals
TXENn
RXDn_0
TXDn_0
TXDn_1
RXDn_1
CRS_DVn
RXERn
DATA
Interface
MDDIS
MDCn
MDINTn
MDIOn
MDIO
Management
Interface
LEDn_2
LEDn_3
Port LEDs/
Controls
ADD[4:0]
TPFOPn
TPFONn
TPFIPn
TPFINn
Network
Interface
VCCIO
+3.3V
OR
+2.5V
VCCD
+2.5V
GNDD
.01uF
Addr &
MDIX/
Contr
Mode Select
MDIX_Enb
Direct Drive
TXCLK
RXCLK
LEDn_1
B3369-01