ST72324BJ2 datasheet(31/188 Pages) STMICROELECTRONICS

Part #	ST72324BJ2

Description	8-bit MCU, 3.8 to 5.5 V operating range with 8 to 32 Kbyte Flash/ROM, 10-bit ADC, 4 timers, SPI, SCI

PDF	188 Pages

Scroll/Zoom	100%

Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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31 / 188 page

ST72324B

Supply, reset and clock management

31/188

Figure 15.

RESET sequences

6.5

System integrity management (SI)

The system integrity management block contains the LVD and auxiliary voltage detector

(AVD) functions. It is managed by the SICSR register.

6.5.1

LVD (low voltage detector)

The LVD function generates a static reset when the VDD supply voltage is below a VIT-

reference value. This means that it secures the power-up as well as the power-down

keeping the ST7 in reset.

The VIT- reference value for a voltage drop is lower than the VIT+ reference value for power-

on in order to avoid a parasitic reset when the MCU starts running and sinks current on the

supply (hysteresis).

The LVD reset circuitry generates a reset when VDD is below:

–VIT+ when VDD is rising

–VIT- when VDD is falling

The LVD function is illustrated in Figure 15.

The voltage threshold can be configured by option byte to be low, medium or high.

VDD

Run

RESET pin

External

Watchdog

Active phase

VIT+(LVD)

VIT-(LVD)

th(RSTL)in

Run

Watchdog underflow

tw(RSTL)out

Run

reset

RESET

source

External

reset

LVD

reset

Watchdog

reset

Internal reset (256 or 4096 TCPU)

Vector fetch

Active

phase

Active

phase

ST72324BJ2 Datasheet(PDF) 31 Page - STMicroelectronics

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