82551IT Datasheet, PDF (44/102 Pages) Intel Corporation – Fast Ethernet PCI Controller

82551IT — Networking Silicon
Figure 11. Auto-Negotiation and Parallel Detect
Force_Fail
6.4
Parallel Detection
Ability detect either by
parallel detect or auto-
negotiation.
Auto-Negotiation
10Base-T or
100Base-TX Link
Ready
FLP capable
Look at Link Pulse;
Auto-Negotiation capable = 0
LINK PASS
Auto-Negotiation capable = 1
Ability Match
Auto-Negotiation Complete bit set
LED Description
The PHY unit supports three LED pins to indicate link status, network activity and network speed.
Each pin can source 10 mA.
• Link: This LED is off until a valid link has been detected. After a valid link has been detected,
the LED will remain on (active-low).
• Activity: This LED blinks on and off when activity is detected on the wire.
• Speed: This LED will be on if a 100BASE-TX link is detected and off if a 10BASE-T link is
detected. If the link fails while in Auto-Negotiation, this LED will keep the last valid link
state. If 100BASE-TX link is forced this LED will be on, regardless of the link status. This
LED will be off if the 10BASE-T link is forced, regardless of the link status.
MDI register 27 in Section 9.3.12, “Register 27: PHY Unit Special Control Register” details the
information for LED function mapping and support enhancements.
Figure 12 provides possible schematic diagrams for configurations using two and three LEDs.
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Datasheet