LAN8742AI-CZ datasheet(37/124 Pages) MICROCHIP

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DS00001989A-page 37

LAN8742A/LAN8742Ai

3.8.1.2

LED1/nINT/nPME Usage with Internal Regulator Enabled (REGOFF Low)

When the LED1/nINT/nPME/REGOFF pin is low during reset, the internal regulator is enabled. After the deassertion of

reset, this pin will first function as LED1 (Link Activity). Upon configuration, it can function as nINT or nPME. Figure 3-

11 illustrates the steps required to program the LED1 pin as nINT or nPME with the internal regulator enabled.

In this configuration, it is recommended not to connect an LED to this pin. Because this pin is active high, the LED will

be lit while waiting for a WoL event.

3.8.1.3

LED2/nINT/nPME Usage with nINTSEL Enabled

When the LED2/nINT/nPME/nINTSEL pin is high during reset, the nINT/REFCLKO pin is configured to function as nINT.

After the deassertion of reset, this pin will first function as LED2 (Link Speed). Upon configuration, it can function as

nPME. It is also possible to configure LED2 as nINT although this would duplicate the function of the nINT/REFCLKO

pin. Figure 3-12 illustrates the steps required to program the LED2 pin as nINT or nPME with nINTSEL enabled.

In this configuration, it is possible for an LED be connected to this pin while it functions as nINT or nPME during a WoL

state. Since the polarity to light the LED is active low, the Link Speed LED will not be lit while waiting for a WoL event.

To provide further flexibility, LED2 can be reconfigured as Link Activity by writing 11b to the LED2 Function Select field

of the Wakeup Control and Status Register (WUCSR). This allows LED2 to function as Link Activity when LED1 cannot

be configured as Link Activity. Link Speed can be easily implemented on the microcontroller using GPIO.

Note:

Refer to Section 3.7.3, "REGOFF: Internal +1.2 V Regulator Configuration" for additional information on

the REGOFF configuration strap.

FIGURE 3-11:

LED1/nINT/nPME/REGOFF WITH INTERNAL REGULATOR ENABLED

Note:

Refer to Section 3.7.4, "nINTSEL: nINT/REFCLKO Configuration" for additional information on the nINT-

SEL configuration strap.

FIGURE 3-12:

LED2/nINT/nPME WITH nINTSEL ENABLED

nRST

LED1/nINT/

WUCSR[14:13]

Link Activity

nINT/nPME

00b

01b/10b

nPME/REGOFF

nRST

LED2/nINT/

WUCSR[12:11]

Link Speed/

nINT/nPME

00b/11b

01b/10b

00b/11b

Link Speed/

Link Activity

00b

Link Activity

nPME/nINTSEL

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