LAN91C111 Datasheet, PDF (34/125 Pages) SMSC Corporation – 10/100 Non-PCI Ethernet Single Chip MAC + PHY

LAN91C111
FIGURE 7-8:
NLP VS. FLP LINK PULSE
TPO±
a.) Normal Link Pulse (NLP)
TPO±
b.) Fast Link Pulse (FLP)
D0
D1
D2
D3
D14
D15
Clock Clock Clock Clock
Data Data Data Data
Clock Clock Clock
Data Data
The Auto-Negotiation algorithm is initiated by any of these events: (1) Auto-Negotiation enabled, (2) a device enters the
Link Fail State, (3) Auto-Negotiation Reset. Once a negotiation has been initiated, the LAN91C111 first determines if the
remote device has Auto-Negotiation capability. If the remote device is not Auto-Negotiation capable and is just transmit-
ting either a 10BASE-T or 100BASE-TX signal, the LAN91C111 will sense that and place itself in the correct mode. If
the LAN91C111 detects FLP's from the remote device, then the remote device is determined to have Auto-Negotiation
capability and the device then uses the contents of the Ml serial port Auto-Negotiation Advertisement register and FLP's
to advertise its capabilities to a remote device. The remote device does the same, and the capabilities read back from
the remote device are stored in the PHY Ml serial port Auto-Negotiation Remote End Capability register. The
LAN91C111 negotiation algorithm then matches it's capabilities to the remote device's capabilities and determines what
mode the device should be configured to according to the priority resolution algorithm defined in IEEE 802.3 Clause 28.
Once the negotiation process is completed, the LAN91C111 then configures itself for either 10 or 100 Mbps mode and
either Full or Half Duplex modes (depending on the outcome of the negotiation process), and it switches to either the
100BASETX or 10BASE-T link integrity algorithms (depending on which mode was enabled by Auto-Negotiation). Refer
to IEEE 802.3 Clause 28 for more details.
7.7.12.5 Auto-Negotiation Outcome Indication
The outcome or result of the Auto-Negotiation process is stored in the speed detect and duplex detect bits in the PHY
MI serial port Status Output register.
7.7.12.6 Auto-Negotiation Status
The status of the Auto-Negotiation process can be monitored by reading the Auto-Negotiation acknowledgment bit in
the Ml serial port Status register. The Ml serial port Status register contains a single Auto-Negotiation acknowledgment
bit which indicates when an Auto-Negotiation has been initiated and successfully completed.
7.7.12.7 Auto-Negotiation Enable
The Auto-Negotiation algorithm can be enabled by setting both the ANEG bit in the MAC Receive/PHY Control Register
and the ANEG_EN bit in the MI PHY Register 0 (Control register). Clearing either of these two bits will turn off Auto-
Negotiation mode. When the Auto-Negotiation algorithm is enabled, the device halts all transmissions including link
pulses for 1200-1500 ms, enters the Link Fail State, and restarts the negotiation process. When Auto-Negotiation mode
is turned on or reset, software driver should wait for at least 1500ms to read the ANEG_ACK bit in the MI PHY Status
Register to determine whether the Auto-Negotiation process has been completed. When the ANEG bit in the
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