Rainbow Electronics ATA6625 - Manual (Page 4)

4
4957E–AUTO–10/07
ATA6623/ATA6625
3.7 Input Pin (TXD)
In Normal mode the TXD pin is the microcontroller interface to control the state of the LIN output.
TXD must be pulled to ground in order to drive the LIN bus low. If TXD is high or unconnected
(internal pull-up resistor), the LIN output transistor is turned off and the bus is in the recessive
state.
3.8 Dominant Time-out Function (TXD)
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
DOM
> 6 ms, the
LIN bus driver is switched to the 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).
3.9 Output Pin (RXD)
The 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
CC
. The AC characteristics are
measured with an external load capacitor of 20 pF.
The output is short-circuit protected. In Unpowered mode (that is, V
S
= 0V), RXD is switched off.
3.10 Enable Input Pin (EN)
This pin controls the Operation mode of the interface. After power up of V
S
(battery), the IC
switches to Fail-safe mode, even if EN is low or unconnected (internal pull-down resistor). If EN
is high, the interface is in Normal mode.
A falling edge at EN while TXD is still high forces the device to Silent mode. A falling edge at EN
while TXD is low forces the device to Sleep mode.