Filter
Top Products
190 Software Developer’s Manual
PHY Functionality and Features
11.6 Determining Link State
The PHY and its link partner determine the type of link established through one of three methods:
• Auto-Negotiation
• Parallel Detection
• Forced Operation
Auto-Negotiation is the only method allowed by the 802.3ab standard for establishing a
1000BASE-T link, although forced operation could be used for test purposes. For 10/100 links, any
of the three methods can be used. The sections that follow discuss each in greater detail.
Figure 11-2 provides an overview of link establishment. First the PHY checks if Auto-Negotiation
is enabled. By default, the PHY supports Auto-Negotiation (PHY register 0, bit 12). If not, the
PHY forces operation as directed. If Auto-Negotiation is enabled, the PHY begins transmitting
Fast Link Pulses (FLPs) and receiving FLPs from its link partner. If FLPs are received by the PHY,
Auto-Negotiation proceeds. It also can receive 100BASE-TX MLT3 and 10BASE-T Normal Link
Pulses (NLPs). If either MLT3 or NLPs are received, it aborts FLP transmission and immediately
brings up the corresponding half-duplex link.
Figure 11-2. Overview of Link Establishment
Power-Up, Reset,
Link Failure
Start
A/N
Enabled
?
Speed
0.13
?
No
Send FLP
Send NLP
0 = 10M
Send IDLES
1 = 100M
Detect
10Mbps
?
Link
Down
No
Link
Up
Yes
Detect
10Mbps
?
Take
Link
Down
No
Take
Link
Up
Yes
Detect
FLP
Auto
Negotiate
Detect
IDLES
Detect
NLP
10M
Half-Duplex
Link
Yes
No
Parallel
Detect
100M
Half-Duplex
Link
Yes
No
Yes
Yes