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ST7LITE0xxx MICROCONTROLLED BALLAST

2.6 STOP STATE

If any abnormal conditions occur (see Section 3) the software will automatically switch itself

into this safety state. The main function is to turn off the half bridge driver by grounding L6384

SD/DT pin. Because the lamp is then off, there is no reason to consume needless microcon-

troller energy. That is why ST7LITE0xxx uses the so-called HALT mode. In this mode, the

processor core and oscillator are turned off to minimize the consumption (consumption in

HALT mode is a few µA).

There are two ways to “wake up” the processor from HALT mode. The first one is to turn off

and on the mains power supply. The second method is using the external interrupt feature on

pin PA7. This feature, briefly described, wakes up the microcontroller when a falling edge

(from 5V to 0V) appears on the pin. In Figure 11 the circuit is shown, which detects the lamp

insertion, connected to the PA7 pin. After waking up, the microcontroller resets itself and the

process starts again from initialization state.