Sleep Mode Controller

Sleep mode is activated by the Wait For Interrupt instruction (WFI). The Idle bits in the Sleep Mode register (SLEEP.IDLE) and the SLEEPDEEP bit of the System Control register of the CPU should be used as argument to select the level of the sleep mode.

There are two main types of sleep mode:

• IDLE mode: The CPU is stopped. Optionally, some synchronous clock domains are stopped, depending on the IDLE argument. Regulator operates in normal mode.
• STANDBY mode: All clock sources are stopped, except those where the RUNSTDBY bit is set. Regulator operates in low-power mode. Before entering standby mode the user must make sure that a significant amount of clocks and peripherals are disabled, so that the voltage regulator is not overloaded.

  Table 1. Sleep Mode Entry and Exit Table

  Mode	Level	Mode Entry	Wake-Up Sources
  IDLE	0	SCR.SLEEPDEEP = 0 SLEEP.IDLE=Level WFI	Synchronous(2) (APB, AHB), asynchronous(1)
  	1		Synchronous (APB), asynchronous
  	2		Asynchronous
  STANDBY		SCR.SLEEPDEEP = 1 WFI	Asynchronous

  Notes:

  1. 1.Asynchronous: interrupt generated on generic clock or external clock or external event.
  2. 2.Synchronous: interrupt generated on the APB clock.

  Table 2. Sleep Mode Overview

  Sleep Mode	CPU Clock	AHB Clock	APB Clock	Oscillators				Main Clock	Regulator Mode	RAM Mode
  				ONDEMAND = 0		ONDEMAND = 1
  				RUNSTDBY=0	RUNSTDBY=1	RUNSTDBY=0	RUNSTDBY=1
  Idle 0	Stop	Run	Run	Run	Run	Run if requested	Run if requested	Run	Normal	Normal
  Idle 1	Stop	Stop	Run	Run	Run	Run if requested	Run if requested	Run	Normal	Normal
  Idle 2	Stop	Stop	Stop	Run	Run	Run if requested	Run if requested	Run	Normal	Normal
  Standby	Stop	Stop	Stop	Stop	Run	Stop	Run if requested	Stop	Low power	Low power