Datasheet

ST7LITE0xY0, ST7LITESxY0
34/124
SYSTEM INTEGRITY MANAGEMENT (Cont’d)
8.4.2 Auxiliary Voltage Detector (AVD)
The Voltage Detector function (AVD) is based on
an analog comparison between a V
IT-(AVD)
and
V
IT+(AVD)
reference value and the V
DD
main sup-
ply voltage (V
AVD
). The V
IT-(AVD)
reference value
for falling voltage is lower than the V
IT+(AVD)
refer-
ence value for rising voltage in order to avoid par-
asitic detection (hysteresis).
The output of the AVD comparator is directly read-
able by the application software through a real
time status bit (AVDF) in the SICSR register. This
bit is read only.
Caution: The AVD functions only if the LVD is en-
abled through the option byte.
8.4.2.1 Monitoring the V
DD
Main Supply
The AVD voltage threshold value is relative to the
selected LVD threshold configured by option byte
(see section 15.1 on page 112).
If the AVD interrupt is enabled, an interrupt is gen-
erated when the voltage crosses the V
IT+(LVD)
or
V
IT-(AVD)
threshold (AVDF bit is set).
In the case of a drop in voltage, the AVD interrupt
acts as an early warning, allowing software to shut
down safely before the LVD resets the microcon-
troller. See Figure 21.
The interrupt on the rising edge is used to inform
the application that the V
DD
warning state is over
Figure 21. Using the AVD to Monitor V
DD
V
DD
V
IT+(AVD)
V
IT-(AVD)
AVDF bit
01
RESET
IF AVDIE bit = 1
V
hyst
AVD INTERRUPT
REQUEST
INTERRUPT Cleared by
V
IT+(LVD)
V
IT-(LVD)
LVD RESET
Early Warning Interrupt
(Power has dropped, MCU not
not yet in reset)
01
hardware
INTERRUPT Cleared by
reset
1