AT91SAM7X128 Atmel, AT91SAM7X128 Datasheet - Page 181

• Manufacturer Part Number: AT91SAM7X128
• Description: MCU 32-Bit 91S ARM7TDMI RISC 128KB Flash 1.8V/3.3V 100-Pin LQFP
• Manufacturer: Atmel

Specifications of AT91SAM7X128

• Package: 100LQFP
• Device Core: ARM7TDMI
• Family Name: 91S
• Maximum Speed: 55 MHz
• Ram Size: 32 KB
• Program Memory Size: 128 KB
• Operating Supply Voltage: 1.8|3.3 V
• Data Bus Width: 32 Bit
• Program Memory Type: Flash
• Number Of Programmable I/os: 62
• Interface Type: CAN/Ethernet/SPI/I2S/TWI/USART/USB
• On-chip Adc: 8-chx10-bit
• Operating Temperature: -40 to 85 °C
• Number Of Timers: 3

25. Power Management Controller (PMC)
25.1
25.2
6120H–ATARM–17-Feb-09
Description
Master Clock Controller
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 PLL.
The Master Clock Controller is made up of a clock selector and a prescaler.
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.
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.
Figure 25-1. Master Clock Controller
• 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,
• UDP Clock (UDPCK), required by USB Device 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.
MAINCK
PLLCK
SLCK
PMC_MCKR
CSS
AT91SAM7X512/256/128 Preliminary
PMC_MCKR
Master Clock
Prescaler
PRES
MCK
To the Processor
Clock Controller (PCK)
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