LAN8740AI-EN datasheet(34/136 Pages) MICROCHIP

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LAN8740A/LAN8740Ai

DS00001987A-page 34

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3.7.2

MODE[2:0]: MODE CONFIGURATION

The MODE[2:0] configuration straps control the configuration of the 10/100 digital block. When the nRST pin is deas-

serted, the register bit values are loaded according to the MODE[2:0] configuration straps. The 10/100 digital block is

then configured by the register bit values. When a soft reset occurs via the Soft Reset bit of the Basic Control Register,

the configuration of the 10/100 digital block is controlled by the register bit values and the MODE[2:0] configuration

straps have no affect.

The device’s mode may be configured using the hardware configuration straps as summarized in Table 3-6. The user

may configure the transceiver mode by writing the SMI registers.

The MODE[2:0] hardware configuration pins are multiplexed with other signals as shown in Table 3-7.

3.7.3

RMIISEL: MII/RMII MODE CONFIGURATION

MII or RMII mode selection is latched on the rising edge of the internal reset (nRST) based on the strapping of the

RMIISEL configuration strap. The default mode is MII (via the internal pull-down resistor). To select RMII mode, pull the

RMIISEL configuration strap high with an external resistor to VDDIO.

When the nRST pin is deasserted, the MIIMODE bit of the Special Modes Register is loaded according to the RMIISEL

configuration strap. The mode is reflected in the MIIMODE bit of the Special Modes Register.

Refer to Section 3.4, "MAC Interface" for additional information on MII and RMII modes.

TABLE 3-6:

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-negoti-

ation 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

110

Power-Down mode. In this mode the transceiver will

wake-up in Power-Down mode. The transceiver can-

not be used when the MODE[2:0] bits are set to this

mode. To exit this mode, the MODE bits in Register

18.7:5 (see Section 4.2.14, "Special Modes Register")

must be configured to some other value and a soft

reset must be issued.

N/A

111

All capable. Auto-negotiation enabled.

X10X

1111

TABLE 3-7:

PIN NAMES FOR MODE BITS

MODE Bit

Pin Name

MODE[0]

RXD0/MODE0

MODE[1]

RXD1/MODE1

MODE[2]

COL/CRS_DV/MODE2

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