SMSC LAN91C111 - Manual (Page 38)

10/100 Non-PCI Ethernet Single Chip MAC + PHY
Datasheet
Revision 1.91 (08-18-08) 38 SMSC LAN91C111 REV C
DATASHEET
100BASE-TX Link Integrity Algorithm -100Mbps
Since 100BASE-TX is defined to have an active idle signal, then there is no need to have separate
link pulses like those defined for 10BASE-T. The LAN91C111 uses the squelch criteria and
descrambler synchronization algorithm on the input data to determine if the device has successfully
established a link with a remote device (called Link Pass State). Refer to IEEE 802.3 for both of these
algorithms for more details.
AutoNegotiation Algorithm
As stated previously, the AutoNegotiation algorithm is used for two purposes: (1) To automatically
configure the device for either 10/100 Mbps and Half/ Full Duplex modes, and (2) to establish an active
link to and from a remote device. The AutoNegotiation algorithm is the same algorithm that is defined
in IEEE 802.3 Clause 28. AutoNegotiation uses a burst of link pulses, called fast link pulses and
referred to as FLP'S, to pass up to 16 bits of signaling data back and forth between the LAN91C111
and a remote device. The transmit FLP pulses meet the templated specified in IEEE 802.3 and shown
in
Figure 7.7 . A timing diagram contrasting NLP's and FLP's is shown in Figure 7.8 .
Figure 7.7 Link Pulse Output Voltage Template - NLP, FLP
0
BT
1.3
BT
2.0
BT
4.0
BT
+50 mV
-50 mV
4.0
BT
42.0
BT
3.1 V
0.5 V/ns
0.5
BT 0.6
BT
300 mV
200 mV
585 mV
+50 mV
-50 mV
2.0
BT 0.85
BT
-3.1 V
0.25
BT