5

4887D–AUTO–12/06

ATA6621

3.7

TXD Dominant Time-out Function

The TXD input has an internal pull-up resistor. An internal timer prevents the bus line from being

driven permanently in the dominant state. If TXD is forced to low longer than t

LIN bus driver is switched to the recessive state. To reset this mode switch (> 10 µs) before

switching LIN to dominant again.

3.8

Output Pin (RXD)

This pin reports the state of the LIN bus to the microcontroller. LIN high (recessive state) is

reported by a high level at RXD, LIN low (dominant state) is reported by a low level at RXD. The

output has an internal pull-up structure with typically 5 k

Ω to V

defined with an external load capacitor of 20 pF.

The output is short-circuit protected. In Unpowered Mode (that is, V

3.9

Enable Input Pin (EN)

This pin controls the operation mode of the interface. If EN is high, the interface is in Normal

Mode, with transmission paths from TXD to LIN and from LIN to RXD both being active. The V

CC

voltage regulator is operating with 5V ±2%/50 mA output capability.

If EN is switched to low while TXD is still high, the device is forced to Silent Mode. No data trans-

mission is then possible and the current consumption is reduced to I

capability of the V

If EN is switched to low while TXD is low, the device is forced to Sleep Mode. No data transmis-

sion is possible and the voltage regulator is switched off.

3.10

Wake Input Pin (WAKE)

This pin is a high voltage input used to wake the device up from Sleep Mode. It is usually con-

nected to an external switch in the application to generate a local wake-up. A pull-up current

source with typically 10 µA is implemented.

If you don’t need a local wake-up in your application, connect pin WAKE directly to pin VS.

3.11

MODE Input Pin

For normal watchdog operation connect pin MODE via an external resistor to GND (see Figure

5-2 on page 23). For debugging your software you can connect pin MODE to 5V and the watch-

dog is switched off.

3.12

TM Input Pin

Pin TM is used in final production measurement at Atmel. In the application it is always con-

nected to GND.