LAN8700I datasheet(46/74 Pages) MICROCHIP

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LAN8700/LAN8700i

DS00002260A-page 46

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5.4.9

CONFIGURATION SIGNALS

The PHY has 11 configuration signals whose inputs should be driven continuously, either by external logic or external

pull-up/pull-down resistors.

5.4.9.1

Physical Address Bus - PHYAD[4:0]

The PHYAD[4:0] signals are driven high or low to give each PHY a unique address. This address is latched into an inter-

nal register at end of hardware reset. In a multi-PHY application (such as a repeater), the controller is able to manage

each PHY via the unique address. Each PHY checks each management data frame for a matching address in the rel-

evant bits. When a match is recognized, the PHY responds to that particular frame. The PHY address is also used to

seed the scrambler. In a multi-PHY application, this ensures that the scramblers are out of synchronization and dis-

perses the electromagnetic radiation across the frequency spectrum.

5.4.9.2

Mode Bus – MODE[2:0]

The MODE[2:0] bus controls the configuration of the 10/100 digital block. When the nRST pin is deasserted, the register

bit values are loaded according to the MODE[2:0] pins. The 10/100 digital block is then configured by the register bit

values. When a soft reset occurs (bit 0.15) as described in Table 5-30, the configuration of the 10/100 digital block is

controlled by the register bit values, and the MODE[2:0] pins have no affect.

FIGURE 5-4:

CONNECTOR LOOPBACK BLOCK DIAGRAM

TABLE 5-48:

MODE[2:0] BUS

Mode [2:0]

Mode Definitions

Default Register Bit Values

[13,12,10,8]

[8,7,6,5]

000

10Base-T Half Duplex. Auto-negotiation disabled.

0000

N/A

001

10Base-T Full Duplex. Auto-negotiation disabled.

0001

N/A

010

100Base-TX Half Duplex. Auto-negotiation disabled.

CRS is active during Transmit & Receive.

1000

N/A

011

100Base-TX Full Duplex. Auto-negotiation disabled.

CRS is active during Receive.

1001

N/A

100

100Base-TX Half Duplex is advertised. Auto-

negotiation enabled.

CRS is active during Transmit & Receive.

1100

0100

101

Repeater mode. Auto-negotiation enabled. 100Base-

TX Half Duplex is advertised.

CRS is active during Receive.

1100

0100

Ethernet Transceiver

10/100

Ethernet

MAC

XFMR

Digital

RXD

TXD

Analog

RJ45 Loopback Cable.

Created by connecting pin 1 to pin 3

and connecting pin 2 to pin 6.

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