ST7MC2N6T3 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
Manufacturer
ST7MC2N6T3
STMicroelectronics
ST7MC2N6T3 Datasheet PDF : 309 Pages
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ST7MC1xx/ST7MC2xx
6.3 SYSTEM INTEGRITY MANAGEMENT (SI)
The System Integrity Management block contains
the Low Voltage Detector (LVD), Auxiliary Voltage
Detector (AVD) and Clock Security System (CSS)
functions. It is managed by the SICSR register.
Note: A reset can also be triggered following the
detection of an illegal opcode or prebyte code. Re-
fer to section 11.2.1 on page 244 for further de-
tails.
6.3.1 Low Voltage Detector (LVD)
The Low Voltage Detector function (LVD) gener-
ates 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 run-
ning 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
Figure 17. Low Voltage Detector vs Reset
The LVD function is illustrated in Figure 17.
Provided the minimum VDD value (guaranteed for
the oscillator frequency) is above VIT-, the MCU
can only be in two modes:
– under full software control
– in static safe reset
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.
The LVD is an optional function which can be se-
lected by option byte.
It is recommended to make sure that the VDD sup-
ply voltage rises monotonously when the device is
exiting from Reset, to ensure the application func-
tions properly.
VDD
VIT+
VIT-
Vhys
RESET
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