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參數(shù)資料
| 型號： | ST72254G1B6 |
| 英文描述： | 8-BIT MCU WITH SINGLE VOLTAGE FLASH MEMORY. ADC. 16-BIT TIMERS. SPI. |
| 中文描述： | 8位單電壓閃存微控制器。 ADC的。 16位定時(shí)器。的SPI。 |
| 文件頁數(shù)： | 56/140頁 |
| 文件大?。?/td> | 1349K |
| 代理商： | ST72254G1B6 |
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ST72104G, ST72215G, ST72216G, ST72254G
22/140
7.4 CLOCK SECURITY SYSTEM (CSS)
The Clock Security System (CSS) protects the
ST7 against main clock problems. To allow the in-
tegration of the security features in the applica-
tions, it is based on a clock filter control and an In-
ternal safe oscillator. The CSS can be enabled or
disabled by option byte.
7.4.1 Clock Filter Control
The clock filter is based on a clock frequency limi-
tation function.
This filter function is able to detect and filter high
frequency spikes on the ST7 main clock.
If the oscillator is not working properly (e.g. work-
ing at a harmonic frequency of the resonator), the
current active oscillator clock can be totally fil-
tered, and then no clock signal is available for the
ST7 from this oscillator anymore. If the original
clock source recovers, the filtering is stopped au-
tomatically and the oscillator supplies the ST7
clock.
7.4.2 Safe Oscillator Control
The safe oscillator of the CSS block is a low fre-
quency back-up clock source (see Figure 13).
If the clock signal disappears (due to a broken or
disconnected resonator...) during a safe oscillator
period, the safe oscillator delivers a low frequency
clock signal which allows the ST7 to perform some
rescue operations.
Automatically, the ST7 clock source switches back
from the safe oscillator if the original clock source
recovers.
Limitation detection
The automatic safe oscillator selection is notified
by hardware setting the CSSD bit of the CRSR
register. An interrupt can be generated if the CS-
SIE bit has been previously set.
These two bits are described in the CRSR register
description.
7.4.3 Low Power Modes
7.4.4 Interrupts
The CSS interrupt event generates an interrupt if
the corresponding Enable Control Bit (CSSIE) is
set and the interrupt mask in the CC register is re-
set (RIM instruction).
Note 1: This interrupt allows to exit from active-halt
mode if this mode is available in the MCU.
Figure 13. Clock Filter Function and Safe Oscillator Function
Mode
Description
WAIT
No effect on CSS. CSS interrupt cause the
device to exit from Wait mode.
HALT
The CRSR register is frozen. The CSS (in-
cluding the safe oscillator) is disabled until
HALT mode is exited. The previous CSS
configuration resumes when the MCU is
woken up by an interrupt with “exit from
HALT mode” capability or from the counter
reset value when the MCU is woken up by a
RESET.
Interrupt Event
Event
Flag
Enable
Control
Bit
Exit
from
Wait
Exit
from
Halt1)
CSS event detection
(safe oscillator acti-
vated as main clock)
CSSD
CSSIE
Yes
No
fOSC/2
fCPU
fOSC/2
fCPU
fSFOSC
S
A
F
E
O
S
CIL
L
AT
O
R
F
UNCT
IO
N
C
L
O
C
K
F
ILTE
R
F
UNCT
IO
N
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| ST72254G1B6/XXX | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:8-BIT MCU WITH SINGLE VOLTAGE FLASH MEMORY, ADC, 16-BIT TIMERS, SPI, IC INTERFACES |
| ST72254G1B7 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:8-BIT MCU WITH SINGLE VOLTAGE FLASH MEMORY. ADC. 16-BIT TIMERS. SPI. |
| ST72254G1B7/XXX | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:8-BIT MCU WITH SINGLE VOLTAGE FLASH MEMORY, ADC, 16-BIT TIMERS, SPI, IC INTERFACES |
| ST72254G1M1 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:8-BIT MCU WITH SINGLE VOLTAGE FLASH MEMORY. ADC. 16-BIT TIMERS. SPI. |
| ST72254G1M1/XXX | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:8-BIT MCU WITH SINGLE VOLTAGE FLASH MEMORY, ADC, 16-BIT TIMERS, SPI, IC INTERFACES |
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