WBLXT9785HE.D0-865114 Cortina Systems Inc, WBLXT9785HE.D0-865114 Datasheet - Page 141

• Manufacturer Part Number: WBLXT9785HE.D0-865114
• Manufacturer: Cortina Systems Inc

Specifications of WBLXT9785HE.D0-865114

• Lead Free Status / RoHS Status: Compliant

LXT9785/LXT9785E
Datasheet
249241, Revision 11.0
16 April 2007
4.9
4.9.1
Figure 27
4.9.2
4.9.2.1
Cortina Systems
100 Mbps Operation
100BASE-X Network Operations
During 100BASE-X operation, the LXT9785/LXT9785E transmits and receives 5-bit
symbols across the network link.
packet. When the MAC is not actively transmitting data, the LXT9785/LXT9785E sends
out Idle symbols on the line.
In 100BASE-TX mode, the device scrambles the data and transmits it to the network
using MLT-3 line code. The MLT-3 signals received from the network are de-scrambled
and decoded, and sent across the RMII to the MAC.
In 100BASE-FX mode, the LXT9785/LXT9785E transmits and receives NRZI signals
across the LVPECL interface. An external 100BASE-FX transceiver module is required to
complete the fiber connection.
As shown in
soon as the LXT9785/LXT9785E detects the start of preamble, it transmits a J/K Start-of-
Stream Delimiter (SSD) symbol to the network. It then encodes and transmits the rest of
the packet, including the balance of the preamble, the Start-of-Frame Delimiter (SFD),
packet data, and CRC. Once the packet ends, the LXT9785/LXT9785E transmits the T/R
End-of-Stream Delimiter (ESD) symbol and then returns to transmitting Idle symbols.
100BASE-X Frame Format
100BASE-X Protocol Sublayer Operations
In a 7-layer communications model, the LXT9785/LXT9785E is a Physical Layer 1 (PHY)
device. The LXT9785/LXT9785E implements the Physical Coding Sublayer (PCS),
Physical Medium Attachment (PMA), and Physical Medium Dependent (PMD) sublayers
of the reference model defined by the IEEE 802.3u specification. The following
paragraphs discuss the LXT9785/LXT9785E operation from the reference model point of
view.
PCS Sublayer
The Physical Coding Sublayer (PCS) provides the RMII interface, as well as the 4B/5B
encoding/decoding function. For 100BASE-TX and 100BASE-FX operation, the PCS
layer provides IDLE symbols to the PMD-layer line driver as long as TxEN is de-asserted.
For 10T operation, the PCS layer merely provides a bus interface and serialization/de-
serialization function. 10T operation does not use the 4B/5B encoder.
®
LXT9785 and LXT9785E Advanced 8-Port 10/100 Mbps PHY Transceivers
Replaced by
/J/K/ code-groups
Start-of-Stream
Delimiter (SSD)
P0
64-Bit Preamble
P1
(8 Octets)
Figure
P6
Delimiter (SFD)
Start-of-Frame
SFD
27, the MAC starts each transmission with a preamble pattern. As
DA
Address (6 Octets each)
Destination and Source
DA
SA
Figure 27
SA
Packet Length
L1
(2 Octets)
shows the structure of a standard frame
L2
(Pad to minimum packet size)
D0
Data Field
D1
Dn
Frame Check Field
(4 Octets)
CRC
4.9 100 Mbps Operation
End-of-Stream Delimiter (ESD)
/T/R/ code-groups
Replaced by
InterFrame Gap / Idle Code
I0
(> 12 Octets)
IFG
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