Datasheet

 2013-2015 Microchip Technology Inc. DS00001987A-page 37
LAN8740A/LAN8740Ai
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-
8 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/TXER/TXD4 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/TXER/TXD4 pin. Figure 3-9 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 3.7.4, "REGOFF: Internal +1.2 V Regulator Configuration" for additional information on
the REGOFF
configuration strap.
FIGURE 3-8: LED1/nINT/nPME/REGOFF WITH INTERNAL REGULATOR ENABLED
Note: Refer to Section 3.7.5, "nINTSEL: nINT/TXER/TXD4 Configuration" for additional information on the nINT-
SEL configuration strap.
FIGURE 3-9: 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