DP83843 datasheet(9/87 Pages) NSC

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1.0 Pin Descriptions (Continued)

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REPEATER

(THIN)

I/O

REPEATER/NODE MODE: Selects 100 Mb/s Repeater mode when set high and

node mode when set low. When set in Repeater mode the DP83843 only supports

100 Mb/s data rates. In Repeater mode (or Node mode with Full Duplex conﬁg-

ured), the Carrier Sense (CRS) output from the DP83843 is asserted due to

receive activity only. In Half Duplex Node mode, CRS is asserted due to either

receive or transmit activity. During repeater mode the heartbeat function(SQE) is

forced off.

The Carrier Integrity Monitor (CIM) function is automatically enabled when this pin

is set high (repeater mode) and disabled when this pin is set low (node mode) in

order to facilitate 802.3u CIM requirements.

There is an internal pullup resistor for this pin which is active during the power-

up/reset period. If this pin is left ﬂoating externally, then the device will conﬁgure to

100 Mb/s Repeater mode as a result of power-up/reset. This pin must be externally

pulled low (typically 10 k

Ω) in order to conﬁgure the DP83843 for Node operation.

The value of this input is latched into the DP83843 at power-up, hardware or soft-

ware reset.

SYMBOL/

(CRS)

I/O, Z

SYMBOL MODE: This active low input allows 100 Mb/s transmit and receive data

streams to bypass all of the transmit and receive operations when set low. Note

that the PCS signals (CRS, RX_DV, RX_ER, and COL) have no meaning during

this mode. During Symbol operation, pins RX_ER/RXD[4] and TX_ER/TXD[4] are

used as the MSB of the 5 bit RX and TX data symbols.

There is an internal pullup resistor for this pin which is active during the power-

up/reset period. If this pin is left ﬂoating externally, then the device will conﬁgure to

normal mode as a result of power-up/reset. This pin must be externally pulled low

(typically 10 k

Ω) in order to conﬁgure the DP83843 for Symbol mode operation.

In Symbol mode this pin will indicate the signal detect status of the TP-PMD (active

high).

This mode has no effect on 10Mb/s operation. The value at this input is latched into

the DP83843 at power-up, hardware or software reset.

SERIAL10

10BASE-T SERIAL/NIBBLE SELECT: With this active low input selected, transmit

and receive data are exchanged serially at a 10 MHz clock rate on the least signiﬁ-

cant bits of the nibble-wide MII data buses, pins TXD[0] and RXD[0] respectively.

This mode is intended for use with the DP83843 connected to a MAC using a 10

Mb/s serial interface. Serial operation is not supported in 100 Mb/s mode, therefore

this input is ignored during 100 Mb/s operation.

There is an internal pullup resistor for this pin which is active during the power-

up/reset period. If this pin is left ﬂoating externally, then the device will conﬁgure to

normal mode as a result of power-up/reset. This pin must be externally pulled low

(typically 10 k

Ω) in order to conﬁgure the DP83843 for Serial MII operation when

running at 10 Mb/s.

The value at this input is latched into the DP83843 at power-up, hardware or soft-

ware reset.

FXEN/

(COL)

I/O, Z

FIBER ENABLE: This active low input allows 100 Mb/s transmit and receive data

streams to bypass the scrambler and descrambler circuits when selected. All PCS

signaling remains active and unaffected during this mode. During this mode, the

internal 100 Mb/s transceiver is disabled, and NRZI data is transmitted and

received via the FXTD/AUITD

+/− and FXRD/AUIRD+/− pins.

There is an internal pullup resistor for this pin which is active during the power-

up/reset period. If this pin is left ﬂoating externally, then the device will conﬁgure to

normal mode as a result of power-up/reset. This pin must be externally pulled low

(typically 10 k

Ω) in order to conﬁgure the DP83843 for 100BASE-FX operation.

The value at this input is latched into the DP83843 at power-up, hardware or soft-

ware reset.

Signal Name

Type

Pin #

Description

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