st10f273m STMicroelectronics, st10f273m Datasheet - Page 108

• Manufacturer Part Number: st10f273m
• Description: 16-bit Mcu With 512 Kbyte Flash Memory And 36 Kbyte Ram
• Manufacturer: STMicroelectronics

Power reduction modes
21
Note:
21.1
21.2
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Power reduction modes
Three different power reduction modes with different levels of power reduction have been
implemented in the ST10F273M. In Idle mode only the CPU is stopped, while peripherals
still operate. In Power-down mode both the CPU and peripherals are stopped. In Standby
mode the main power supply (V
remains powered via V
Idle and Power-down modes are software activated by a protected instruction and are
terminated in different ways as described in the following sections.
Standby mode is entered by simply removing V
All external bus actions are completed before Idle or Power-down mode is entered.
However, Idle or Power-down mode is not entered if READY is enabled, but has not been
activated (driven low for negative polarity, or driven high for positive polarity) during the last
bus access.
Idle mode
Idle mode is entered by running the IDLE protected instruction. The CPU operation is
stopped and the peripherals still run.
Idle mode is terminated by any interrupt request. Whether or not the interrupt is serviced,
the instruction following the IDLE instruction will be executed after the return from interrupt
(RETI) instruction, and the CPU then resumes the normal program.
Power-down mode
Power-down mode starts by running the PWRDN protected instruction. The internal clock is
stopped and all MCU parts including the watchdog timer are on hold. The only exception
could be the Real Time Clock if programmed accordingly in conjuction with selecting one of
the two oscillator circuits (either the main or the 32 kHz on-chip oscillator).
If the Real Time Clock module is used when the device is in Power-down mode, a reference
clock is needed. In this case, two possible configurations may be selected by the user
application according to the desired level of power reduction:
●
●
There are two different operating Power-down modes: protected mode and interruptible
mode.
A 32 kHz crystal is connected to the on-chip low-power oscillator (pins XTAL3 / XTAL4)
and running. In this case the main oscillator is stopped when Power-down mode is
entered, while the Real Time Clock continues counting using a 32 kHz clock signal as
reference. The presence of a running low-power oscillator is detected after the Power-
on: This clock is immediately assumed (if present, or as soon as it is detected) as
reference for the Real Time Clock counter and it will be maintained indefinitely (unless
specifically disabled via software).
Only the main oscillator is running (XTAL1 / XTAL2 pins). In this case the main
oscillator is not stopped when Power-down is entered, and the Real Time Clock
continues counting using the main oscillator clock signal as reference.
STBY
dedicated power pin.
DD
) can be turned off while a portion of the internal RAM
DD
, holding the MCU under reset state.
ST10F273M