
22
MD400184/A
84221
FLP pulses meet the template specified in IEEE 802.3 and
shown in Figure 7.  A timing diagram contrasting NLP’s
and FLP’s is shown in Figure 8.
The AutoNegotiation algorithm is initiated by any of the
following events:
 Powerup
 Device Reset
 AutoNegotiation Reset
 Entering the Link Fail state
Once a negotiation has been initiated, the 84221 first
determines if the remote device has AutoNegotiation
capability.  If the device is not AutoNegotiation capable
and is just transmitting either a 10Base-T or 100Base-TX
signal, the 84221 will sense that and place itself in the
correct mode.  If the 84221 detects FLP’s from the remote
device, then the remote device is determined to have
AutoNegotiation capability and  the device then uses the
contents 
of 
the 
MI 
serial 
Advertisement register and FLP’s to advertise it’s
capabilies to a remote device.  The remote device does
the same, and the capabilities read back from the remote
device are stored in the MI serial port AutoNegotiation
Remote End Capability register.  The 84221 negotiation
algorithm then matches it’s capabilities to the remote
devices capabilities and determines to what mode the
device should be configured according to the priority
resolution algorithm defined in IEEE 802.3 Clause 28.
Once the negotiation process is completed, the 84221
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 100Base-TX or 10Base-T link integrity
algorithms (depending on which mode was enabled by
AutoNegotiation).  Refer to IEEE 802.3 Clause 28 for more
details.
port 
AutoNegotiation
2.13.5  AutoNegotiation Outcome Indication
The outcome or result of the AutoNegotiation process is
stored in the speed detect and duplex detect bits in the MI
serial port Status Output register.
2.13.6  AutoNegotiation Status
The status of the AutoNegotiation process can be
monitored by reading the AutoNegotiation Acknow-
ledgement Bit  in  the MI serial port Status register.  
2.13.7  AutoNegotiation Enable
The AutoNegotiation algorithm can be enabled (or
restarted) by setting the AutoNegotiation enable bit in the
MI serial port Control register or by asserting the ANEG
pin.  The AutoNegotiatiopn enable bit and ANEG pin both
have to be high to enable AutoNegotiation.  When the
AutoNegotiation 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 the AutoNegotiation algorithm is disabled,
the selection of 100 Mbps or 10 Mbps mode is determined
by the speed select bit in the MI serial port Control
register, and the selection of Half or Full Duplex is
determined by the duplex select bit in the MI serial port
Control register.
2.13.8  AutoNegotiation Reset
The AutoNegotiation algorithm can be initiated at any time
by setting the AutoNegotiation reset bit in the MI serial
port Control register.
2.13.9  Link Indication 
Receive link detect activity can be monitored through the
link detect bit in the MI serial port Status and Status
Output registers or it can also be programmed to appear
on LED status pins by appropriately setting the
programmable LED select bits in the MI serial port
Configuration 2 register as shown in Table 3.  Whenever
the LED Status pins are programmed to be a link detect
output, these pins are asserted low whenever the device
is in the Link Pass state.
2.13.10  Link Disable
The link integrity function can be disabled by setting the
link disable bit in the MI serial port Configuration 1
register.  When the link integrity function is disabled, the
device is forced into the Link Pass state, configures itself
for Half/Full Duplex based on the value of the duplex bit in
the MI serial port Control register, configures itself for 100/
10 Mbps operation based on the values of the speed bit in
the MI serial port Control register, and continues to
transmit NLP’s or TX idle patterns, depending on whether
the device is in 10 or 100 Mbps mode.
2.14  JABBER 
2.14.1  100 Mbps
The jabber function is disabled in the 100 Mbps mode.
2.14.2  10 Mbps
A jabber condition occurs when the transmit packet
exceeds a predetermined length. When jabber is
detected, the TP transmit outputs  are forced to the idle
state, collision is asserted,  and jabber register bits in the
MI serial port Status and Channel Status Output registers
are set.