Rainbow Electronics ATA6624 - Manual (Page 5)

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4986F–AUTO–07/08
ATA6622/ATA6624/ATA6626
3.7 Input/Output Pin (TXD)
In Normal Mode the TXD pin is the microcontroller interface used to control the state of the LIN
output. TXD must be pulled to ground in order to have a low LIN-bus. If TXD is high or uncon-
nected (internal pull-up resistor), the LIN output transistor is turned off, and the bus is in
recessive state. During Fail-safe Mode, this pin is used as output. It is current-limited to < 8 mA.
and is latched to low if the last wake-up event was from pin WAKE or KL_15.
3.8 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 dominant state. If TXD is forced to low for longer than t
DOM
> 6 ms, the
LIN-bus driver is switched to recessive state. Nevertheless, when switching to Sleep Mode, the
actual level at the TXD pin is relevant.
To reactivate the LIN bus driver, switch TXD to high (> 10 µs).
The time-out function is disabled in the ATA6626. Switching to dominant level on the LIN bus
occurs without any time limitations.
3.9 Output Pin (RXD)
The Output 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 VCC. The AC characteristics
can be defined with an external load capacitor of 20 pF.
The output is short-circuit protected. RXD is switched off in Unpowered Mode (i.e., V
S
= 0V).
3.10 Enable Input Pin (EN)
The Enable Input 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 active. The
VCC voltage regulator operates with 3.3V/5V/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
VS
typ. 57 µA. The VCC
regulator has its full functionality.
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.
3.11 Wake Input Pin (WAKE)
The Wake Input pin is a high-voltage input used to wake up the device from Sleep Mode or
Silent Mode. It is usually connected to an external switch in the application to generate a local
wake-up. A pull-up current source, typically 10 µA, is implemented.
If a local wake-up is not needed for the application, connect the Wake pin directly to the VS pin.
3.12 Mode Input Pin (MODE)
Connect the MODE pin directly or via an external resistor to GND for normal watchdog opera-
tion. To debug the software of the connected microcontroller, connect MODE pin to 3.3V/5V and
the watchdog is switched off.