at91sam9263 ATMEL Corporation, at91sam9263 Datasheet - Page 352

• Manufacturer Part Number: at91sam9263
• Description: At91 Arm Thumb Microcontrollers
• Manufacturer: ATMEL Corporation

27. Power Management Controller (PMC)
27.1
27.2
352
Description
Master Clock Controller
AT91SAM9263 Preliminary
The Power Management Controller (PMC) optimizes power consumption by controlling all sys-
tem and user peripheral clocks. The PMC enables/disables the clock inputs to many of the
peripherals and the ARM Processor.
The Power Management Controller provides the following clocks:
The Master Clock Controller provides selection and division of the Master Clock (MCK). MCK is
the clock provided to all the peripherals and the memory controller.
The Master Clock is selected from one of the clocks provided by the Clock Generator. Selecting
the Slow Clock provides a Slow Clock signal to the whole device. Selecting the Main Clock
saves power consumption of the PLLs.
The Master Clock Controller is made up of a clock selector and a prescaler. It also contains a
Master Clock divider which allows the processor clock to be faster than the Master Clock.
The Master Clock selection is made by writing the CSS field (Clock Source Selection) in
PMC_MCKR (Master Clock Register). The prescaler supports the division by a power of 2 of the
selected clock between 1 and 64. The PRES field in PMC_MCKR programs the prescaler. The
Master Clock divider can be programmed through the MDIV field in PMC_MCKR.
Each time PMC_MCKR is written to define a new Master Clock, the MCKRDY bit is cleared in
PMC_SR. It reads 0 until the Master Clock is established. Then, the MCKRDY bit is set and can
trigger an interrupt to the processor. This feature is useful when switching from a high-speed
clock to a lower one to inform the software when the change is actually done.
• MCK, the Master Clock, programmable from a few hundred Hz to the maximum operating
• Processor Clock (PCK), switched off when entering processor in idle mode.
• Peripheral Clocks, typically MCK, provided to the embedded peripherals (USART, SSC, SPI,
• UHP Clock (UHPCK), required by USB Host Port operations.
• Programmable Clock Outputs can be selected from the clocks provided by the clock
frequency of the device. It is available to the modules running permanently, such as the AIC
and the Memory Controller.
TWI, TC, MCI, 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.
generator and driven on the PCKx pins.
6249D–ATARM–20-Dec-07