ST ST10F276E - Idle Mode; Table 66. Power Reduction Modes Summary

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UM0404 Power reduction modes
Note: If the on-chip low-power oscillator is not in use, the Real Time Clock module can only be
driven by the main oscillator: in this case it is not possible to turn off the main power supply
(V
DD
) of the device, since the main oscillator circuitry would stop working. In this case,
standard Power Down mode is recommended (V
DD
on, so RTC can be driven by the main
oscillator).
24.1 Idle mode
The power consumption of the ST10F276 microcontroller can be decreased by entering Idle
mode. In this mode all peripherals, including the watchdog timer, continue to operate
normally, only the CPU operation is halted.
Idle mode is entered after the IDLE instruction has been executed and the instruction before
the IDLE instruction has been completed. To prevent unintentional entry into Idle mode, the
IDLE instruction has been implemented as a protected 32-bit instruction.
Idle mode is terminated by interrupt request from any enabled interrupt source whose
individual Interrupt Enable flag has been set before the Idle mode was entered, regardless
of bit IEN.
For a request selected for CPU interrupt service the associated interrupt service routine is
entered if the priority level of the requesting source is higher than the current CPU priority
and the interrupt system is globally enabled. After the RETI (Return from Interrupt)
instruction of the interrupt service routine is executed, the CPU continues executing the
program with the instruction following the IDLE instruction. Otherwise, if the interrupt
request cannot be serviced because of a too low priority or a globally disabled interrupt
system, the CPU immediately resumes normal program execution with the instruction
following the IDLE instruction.
Table 66. Power reduction modes summary
Mode
V
DD
V
STBY
CPU
Peripherals
RTC
Main OSC
32 kHz OSC
STBY XRAM
XRAM
Idle
on on off on off on off biased biased
on on off on on on on biased biased
on on off on on on off biased biased
Power Down
on on off off off off off biased biased
on on off off on on off biased biased
on on off off on off on biased biased
Stand-by
off on off off off off off biased off
off on off off on off on biased off