参数资料
型号: ST72F321J9T7
厂商: STMICROELECTRONICS
元件分类: 微控制器/微处理器
英文描述: 8-BIT, FLASH, 8 MHz, MICROCONTROLLER, PQFP44
封装: 10 X 10 MM, PLASTIC, TQFP-44
文件页数: 95/176页
文件大小: 1112K
代理商: ST72F321J9T7
ST72321J
25/176
6.4 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.
6.4.1 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
The LVD function is illustrated in Figure 13.
The voltage threshold can be configured by option
byte to be low, medium or high.
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.
Figure 13. Low Voltage Detector vs Reset
VDD
VIT+
RESET
VIT-
Vhys
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