LXT971A 3.3V Dual-Speed Fast Ethernet Transceiver
Table 10. Carrier Sense, Loopback, and Collision Conditions
Speed
Duplex Condition
Carrier Sense
Test
1
Loopback
Operational
Loopback
Collision
100 Mbps
Full-Duplex
Half-Duplex
Full-Duplex
Receive Only
Transmit or Receive
Receive Only
Transmit or Receive
Transmit or Receive
Yes
No
Yes
Yes
No
No
No
No
Yes
No
None
Transmit and Receive
None
Transmit and Receive
Transmit and Receive
10 Mbps
Half-Duplex,
Register bit 16.8 = 0
Half-Duplex,
Register bit 16.8 = 1
1. Test Loopback is enabled when 0.14 = 1
3.7
3.7.1
100 Mbps Operation
100BASE-X Network Operations
During 100BASE-X operation, the LXT971A transmits and receives 5-bit symbols across the
network link.
shows the structure of a standard frame packet. When the MAC is not
actively transmitting data, the LXT971A sends out Idle symbols on the line.
In 100BASE-TX mode, the LXT971A scrambles and transmits the data to the network using MLT-
3 line code (Figure
MLT-3 signals received from the network are de-scrambled,
decoded, and sent across the MII to the MAC.
In 100BASE-FX mode, the LXT971A transmits and receives NRZI signals across the LVPECL
interface. An external 100FX transceiver module is required to complete the fiber connection. To
enable 100BASE-FX operation, auto-negotiation must be disabled and FX selected.
Figure 14. 100BASE-X Frame Format
64-Bit Preamble
(8 Octets)
Destination and Source
Address (6 Octets each)
Packet Length
(2 Octets)
Data Field
Frame Check Field InterFrame Gap / Idle Code
(Pad to minimum packet size)
(4 Octets)
(> 12 Octets)
P0
P1
P6
SFD
DA
DA
SA
SA
L1
L2
D0
D1
Dn
CRC
I0
IFG
Replaced by
/J/K/ code-groups
Start-of-Stream
Delimiter (SSD)
Start-of-Frame
Delimiter (SFD)
Replaced by
/T/R/ code-groups
End-of-Stream Delimiter (ESD)
36
Datasheet
Document #: 249414
Revision #: 002
Rev. Date: August 7, 2002
INTEL [ INTEL CORPORATION ]
