LAN88730 datasheet(32/82 Pages) MICROCHIP

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LAN88730

DS60001256B-page 32

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3.7.4

nINTSEL: nINT/TXER/TXD4 CONFIGURATION

The nINT, TXER, and TXD4 functions share a common pin. There are two functional modes for this pin, the TXER/TXD4

mode and nINT (interrupt) mode. The nINTSEL configuration strap is latched at POR and on the rising edge of the nRST.

By default, nINTSEL is configured for nINT mode via the internal pull-up resistor.

3.8

Miscellaneous Functions

3.8.1

LEDS

Two LED signals are provided as a convenient means to indicate the transceiver's mode of operation. All LED signals

are either active high or active low as described in Section 3.8.1.1, "LED1 Polarity Selection" and Section 3.8.1.2, "nINT-

SEL and LED2 Polarity Selection".

The LED1 output is driven active whenever the device detects a valid link, and blinks when CRS is active (high) indicat-

ing activity.

The LED2 output is driven active when the operating speed is 100 Mbps. This LED will go inactive when the operating

speed is 10 Mbps or during line isolation.

3.8.1.1

LED1 Polarity Selection

The LED1 output will automatically change its polarity based on the presence of an external pull-up resistor. If the LED1

pin is pulled high to VDD2A by an external pull-up resistor, then the LED1 output will be active low. If the LED1 pin is

pulled low by the internal pull-down resistor, the LED1 output will then be an active high output. Figure 3-7 details the

LED1 polarity.

Note:

Because the nINTSEL configuration strap shares functionality with the LED2 pin, proper consideration

must also be given to the LED polarity. Refer to Section 3.8.1.2, "nINTSEL and LED2 Polarity Selection"

for additional information on the relation between nINTSEL and the LED2 polarity.

Note:

When pulling the LED1 and LED2 pins high, they must be tied to VDD2A, NOT VDDIO.

FIGURE 3-7:

LED1 POLARITY CONFIGURATION

LED1

~270



LED output = Active High

~270



VDD2A

LED output = Active Low

LED1

10K

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