LAN91C111 datasheet(33/125 Pages) MICROCHIP

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DS00002276A-page 33

LAN91C111

7.7.12.3

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.

7.7.12.4

Auto-Negotiation Algorithm

As stated previously, the Auto-Negotiation 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

Auto-Negotiation algorithm is the same algorithm that is defined in IEEE 802.3 Clause 28. Auto-Negotiation 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

1.3

2.0

4.0

+50 mV

-50 mV

4.0

42.0

3.1 V

0.5 V/ns

0.5

BT 0.6

300 mV

200 mV

585 mV

+50 mV

-50 mV

2.0

0.85

-3.1 V

0.25

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