ST72321BR9-AUTO View Datasheet(PDF) - STMicroelectronics

Part Name

Description

MFG CO.

ST72321BR9-AUTO

8-bit MCU for automotive with 32 to 60 Kbyte Flash/ROM, ADC, 5 timers, SPI, SCI, I2C interface

STMicroelectronics 

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ST72321Bxxx-Auto

Figure 13. RESET sequences

VDD

VIT+(LVD)

VIT-(LVD)

RUN

LVD

RESET

Active Phase

EXTERNAL

RESET

SOURCE

RESET PIN

WATCHDOG

RESET

Supply, reset and clock management

RUN

SHORT EXT.

RESET

Active

Phase

RUN

LONG EXT.

RESET

Active

Phase

RUN

WATCHDOG

RESET

Active

Phase

RUN

tw(RSTL)out

th(RSTL)in

tw(RSTL)out

th(RSTL)in

DELAY

tw(RSTL)out

WATCHDOG UNDERFLOW

INTERNAL RESET (256 or 4096 TCPU)

VECTOR FETCH

6.6

6.6.1

System integrity management (SI)

The System Integrity Management block contains the Low Voltage Detector (LVD) and

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

Low voltage detector (LVD)

The low voltage detector function (LVD) 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 14.

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

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