ST7DALIF2 datasheet(42/171 Pages) STMICROELECTRONICS

42 / 171 page

Supply, reset and clock management

ST7DALIF2

42/171

Figure 17.

Reset and supply management block diagram

9.7.2

Auxiliary voltage detector (AVD)

The Voltage Detector function (AVD) is based on an analog comparison between a VIT-(AVD)

and VIT+(AVD) reference value and the VDD main supply voltage (VAVD). The VIT-(AVD)

reference value for falling voltage is lower than the VIT+(AVD) reference value for rising

voltage in order to avoid parasitic detection (hysteresis).

The output of the AVD comparator is directly readable 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 enabled through the option byte.

Monitoring the VDD main supply

The AVD voltage threshold value is relative to the selected LVD threshold configured by

option byte (see Section 22.1 on page 161).

If the AVD interrupt is enabled, an interrupt is generated when the voltage crosses the

VIT+(LVD) or VIT-(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 microcontroller. See Figure 18.

LOW VOLTAGE

DETECTOR

(LVD)

AUXILIARY VOLTAGE

DETECTOR

(AVD)

RESET

VSS

VDD

RESET SEQUENCE

MANAGER

(RSM)

AVD Interrupt Request

SYSTEM INTEGRITY MANAGEMENT

WATCHDOG

SICSR

TIMER (WDG)

AVDIE

AVDF

STATUS FLAG

LVDRF

LOCKED

WDGRF

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