Atmel Xplained Pro Evaluation Kit for the ATSAMD21J18A Microcontroller ATSAMD21-XPRO ATSAMD21-XPRO Data Sheet
Product codes
ATSAMD21-XPRO
106
Atmel | SMART SAM D21 [DATASHEET]
Atmel-42181C–SAM-D21_Datasheet–07/2014
15.
PM – Power Manager
15.1 Overview
The Power Manager (PM) controls the reset, clock generation and sleep modes of the microcontroller.
Utilizing a main clock chosen from a large number of clock sources from the GCLK, the clock controller provides
synchronous system clocks to the CPU and the modules connected to the AHB and the APBx bus. The synchronous
system clocks are divided into a number of clock domains; one for the CPU and AHB and one for each APBx. Any
synchronous system clock can be changed at run-time during normal operation. The clock domains can run at different
speeds, enabling the user to save power by running peripherals at a relatively low clock frequency, while maintaining
high CPU performance. In addition, the clock can be masked for individual modules, enabling the user to minimize power
consumption.
synchronous system clocks to the CPU and the modules connected to the AHB and the APBx bus. The synchronous
system clocks are divided into a number of clock domains; one for the CPU and AHB and one for each APBx. Any
synchronous system clock can be changed at run-time during normal operation. The clock domains can run at different
speeds, enabling the user to save power by running peripherals at a relatively low clock frequency, while maintaining
high CPU performance. In addition, the clock can be masked for individual modules, enabling the user to minimize power
consumption.
Before entering the STANDBY sleep mode the user must make sure that a significant amount of clocks and peripherals
are disabled, so that the voltage regulator is not overloaded. This is because during STANDBY sleep mode the internal
voltage regulator will be in low power mode.
are disabled, so that the voltage regulator is not overloaded. This is because during STANDBY sleep mode the internal
voltage regulator will be in low power mode.
Various sleep modes and clock gating are provided in order to fit power consumption requirements. This enables the
microcontroller to stop unused modules to save power. In ACTIVE mode, the CPU is executing application code. When
the device enters a sleep mode, program execution is stopped and some modules and clock domains are automatically
switched off by the PM according to the sleep mode. The application code decides which sleep mode to enter and when.
Interrupts from enabled peripherals and all enabled reset sources can restore the microcontroller from a sleep mode to
ACTIVE mode.
microcontroller to stop unused modules to save power. In ACTIVE mode, the CPU is executing application code. When
the device enters a sleep mode, program execution is stopped and some modules and clock domains are automatically
switched off by the PM according to the sleep mode. The application code decides which sleep mode to enter and when.
Interrupts from enabled peripherals and all enabled reset sources can restore the microcontroller from a sleep mode to
ACTIVE mode.
The PM also contains a reset controller, which collects all possible reset sources. It issues a microcontroller reset and
sets the device to its initial state, and allows the reset source to be identified by software.
sets the device to its initial state, and allows the reset source to be identified by software.
15.2 Features
z
Reset control
z
Reset the microcontroller and set it to an initial state according to the reset source
z
Multiple reset sources
z
Power reset sources: POR, BOD12, BOD33
z
User reset sources: External reset (RESET), Watchdog Timer reset, software reset
z
Reset status register for reading the reset source from the application code
z
Clock control
z
Controls CPU, AHB and APB system clocks
z
Multiple clock sources and division factor from GCLK
z
Clock prescaler with 1x to 128x division
z
Safe run-time clock switching from GCLK
z
Module-level clock gating through maskable peripheral clocks
z
Power management control
z
Sleep modes: IDLE, STANDBY
z
SleepWalking support on GCLK clocks