STM8S207xx, STM8S208xx
Product overview
4.6
Power management
For efficent power management, the application can be put in one of four different low-power
modes. You can configure each mode to obtain the best compromise between lowest power
consumption, fastest start-up time and available wakeup sources.
●
Wait mode: In this mode, the CPU is stopped, but peripherals are kept running. The
wakeup is performed by an internal or external interrupt or reset.
●
Active halt mode with regulator on: In this mode, the CPU and peripheral clocks are
stopped. An internal wakeup is generated at programmable intervals by the auto wake
up unit (AWU). The main voltage regulator is kept powered on, so current consumption
is higher than in active halt mode with regulator off, but the wakeup time is faster.
Wakeup is triggered by the internal AWU interrupt, external interrupt or reset.
●
●
Active halt mode with regulator off: This mode is the same as active halt with
regulator on, except that the main voltage regulator is powered off, so the wake up time
is slower.
Halt mode: In this mode the microcontroller uses the least power. The CPU and
peripheral clocks are stopped, the main voltage regulator is powered off. Wakeup is
triggered by external event or reset.
4.7
Watchdog timers
The watchdog system is based on two independent timers providing maximum security to
the applications.
Activation of the watchdog timers is controlled by option bytes or by software. Once
activated, the watchdogs cannot be disabled by the user program without performing a
reset.
Window watchdog timer
The window watchdog is used to detect the occurrence of a software fault, usually
generated by external interferences or by unexpected logical conditions, which cause the
application program to abandon its normal sequence.
The window function can be used to trim the watchdog behavior to match the application
perfectly.
The application software must refresh the counter before time-out and during a limited time
window.
A reset is generated in two situations:
1. Timeout: At 16 MHz CPU clock the time-out period can be adjusted between 75 µs up
to 64 ms.
2. Refresh out of window: The downcounter is refreshed before its value is lower than the
one stored in the window register.
Doc ID 14733 Rev 9
17/103
STMICROELECTRONICS [ ST ]
