Atmel SAM4S Xplained Pro Starter Kit Atmel ATSAM4S-XSTK ATSAM4S-XSTK Data Sheet

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SAM4S [DATASHEET]

11100E–ATARM–24-Jul-13

The Power Management Controller (PMC) optimizes power consumption by controlling all system 
and user peripheral clocks. The PMC enables/disables the clock inputs to many of the peripherals 
and the Cortex-M4 Processor.

The Supply Controller selects between the 32 kHz RC oscillator or the slow crystal oscillator. The 
unused oscillator is disabled automatically so that power consumption is optimized.

By default, at start-up the chip runs out of the Master Clock using the Fast RC Oscillator running at 4 
MHz.

The user can trim the 8 and 4 MHz RC Oscillator frequencies by software.

The Power Management Controller provides the following clocks:



MCK, the Master Clock, programmable from a few hundred Hz to the maximum operating 
frequency of the device. It is available to the modules running permanently, such as the 
Enhanced Embedded Flash Controller.



Processor Clock (HCLK) , automatically switched off when entering the processor in Sleep 
Mode.



Free running processor Clock (FCLK) 



The Cortex-M4 SysTick external clock 



UDP Clock (UDPCK), required by USB Device Port operations.



Peripheral Clocks, typically MCK, provided to the embedded peripherals (USART, SPI, TWI, 
TC, etc.) and independently controllable. In order to reduce the number of clock names in a 
product, the Peripheral Clocks are named MCK in the product datasheet.



Programmable Clock Outputs can be selected from the clocks provided by the clock generator 
and driven on the PCKx pins.



Write Protected Registers

The Power Management Controller also provides the following operations on clocks:



A main crystal oscillator clock failure detector.



A frequency counter on main clock and an on-the-fly adjustable main RC oscillator frequency.