ST72521 STMICROELECTRONICS [STMicroelectronics], ST72521 Datasheet - Page 28

• Manufacturer Part Number: ST72521
• Description: 8-BIT MCU WITH NESTED INTERRUPTS, FLASH, 10-BIT ADC, FIVE TIMERS, SPI, SCI, I2C, CAN INTERFACE
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

ST72521
6.4 SYSTEM INTEGRITY MANAGEMENT (SI)
The System Integrity Management block contains
the Low Voltage Detector (LVD), Auxiliary Voltage
Detector (AVD) functions and Clock Security Sys-
tem (CSS). It is managed by the SICSR register.
6.4.1 Low Voltage Detector (LVD)
The Low Voltage Detector function (LVD) gener-
ates a static reset when the V
below a V
secures the power-up as well as the power-down
keeping the ST7 in reset.
The V
than the V
to avoid a parasitic reset when the MCU starts run-
ning and sinks current on the supply (hysteresis).
The LVD Reset circuitry generates a reset when
V
The LVD function is illustrated in
Figure 14. Low Voltage Detector vs Reset
28/211
DD
– V
– V
RESET
is below:
IT-
IT+
IT-
V
V
reference value for a voltage drop is lower
when V
when V
IT-
IT+
IT+
IT-
reference value for power-on in order
reference value. This means that it
V
DD
DD
DD
is falling
is rising
DD
supply voltage is
Figure
14.
Provided the minimum V
the oscillator frequency) is above V
can only be in two modes:
In these conditions, secure operation is always en-
sured for the application without the need for ex-
ternal reset hardware.
During a Low Voltage Detector Reset, the RESET
pin is held low, thus permitting the MCU to reset
other devices.
Notes:
The LVD allows the device to be used without any
external RESET circuitry.
If the medium or low thresholds are selected, the
detection may occur outside the specified operat-
ing voltage range. Below 3.8V, device operation is
not guaranteed.
The LVD is an optional function which can be se-
lected by option byte.
V
– under full software control
– in static safe reset
hys
DD
value (guaranteed for
IT-
, the MCU