80221 datasheet(24/91 Pages) LSI

24 / 91 page

80220/80221

MD400159/E

3.13.7 AutoNegotiation Enable

The AutoNegotiation algorithm can be enabled (or re-

started) by setting the AutoNegotiation enable bit in the MI

serial port Control register. 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 modes 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.

3.13.8 AutoNegotiation Reset

The AutoNegotiation algorithm can be initiated at any time

by setting the AutoNegotiation reset bit in the MI serial port

Control register.

3.13.9 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 the

PLED3 or PLED0 pin by appropriately setting the pro-

grammable LED output select bits in the MI serial port

Configuration 2 register as shown in Table 5. When either

the PLED3 or PLED0 pins are programmed to be a link

detect output, these pins are asserted low whenever the

device is in the Link Pass State. The PLED3 output is open

drain with pullup resistor and can drive an LED from VCC;

The PLED0 output has both pullup and pulldown driver

transistors in addition to a weak pullup resistor, so it can

drive an LED from either VCC or GND. Both PLED3 and

PLED0 can also drive another digital input. Refer to the

LED Driver Section (3.23) for a description on how to

program the PLED[3:0] pins and their defaults.

3.13.10 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.

3.13.11 100Base-T4 Capability

The 80221 has the ability to advertise and detect 100Base-

T4 capability in addition to 100Base-TX Full/Half Duplex

and 10Base-T Full/Half Duplex capability. Refer to the

100Base-T4 Interface section for more details.

3.14 JABBER

3.14.1 100 Mbps

Jabber function is disabled in the 100 Mbps mode.

3.14.2 10 Mbps

Jabber condition occurs when the transmit packet ex-

ceeds a predetermined length. When jabber is detected,

the TP transmit outputs

are forced to the idle state,

collision is asserted, and register bits in the MI serial port

Status and Status Output registers are set.

3.14.3 Jabber Disable

The jabber function can be disabled by setting the jabber

disable bit in the MI serial port Configuration 2 register.

3.15 RECEIVE POLARITY CORRECTION

3.15.1 100 Mbps

No polarity detection or correction is needed in 100 Mbps

mode.

3.15.2 10 Mbps

The polarity of the signal on the TP receive input is

continuously monitored. If either 3 consecutive link pulses

or one SOI pulse indicates incorrect polarity on the TP

receive input, the polarity is internally determined to be

incorrect, and a reverse polarity bit is set in the MI serial

port Status Output register.

The 80220/80221 will automatically correct for the reverse

polarity condition provided that the autopolarity feature is

not disabled.

3.15.3 Autopolarity Disable

The autopolarity feature can be disabled by setting the

autopolarity disable bit in the MI serial port Configuration

2 register.

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