sam4s8c ATMEL Corporation, sam4s8c Datasheet - Page 39

• Manufacturer Part Number: sam4s8c
• Description: At91sam Arm-based Flash Mcu
• Manufacturer: ATMEL Corporation

10.5
11100AS–ATARM–27-Oct-11
Clock Generator
The reset circuitry is based on a zero-power power-on reset cell and a brownout detector cell.
The zero-power power-on reset allows the Supply Controller to start properly, while the soft-
ware-programmable brownout detector allows detection of either a battery discharge or main
voltage loss.
The Slow Clock generator is based on a 32 kHz crystal oscillator and an embedded 32 kHz RC
oscillator. The Slow Clock defaults to the RC oscillator, but the software can enable the crystal
oscillator and select it as the Slow Clock source.
The Supply Controller starts up the device by sequentially enabling the internal power switches
and the Voltage Regulator, then it generates the proper reset signals to the core power supply.
It also enables to set the system in different low-power modes and to wake it up from a wide
range of events.
The Clock Generator is made up of:
• One Low-power 32768 Hz Slow Clock Oscillator with bypass mode
• One Low-power RC Oscillator
• One 3-20 MHz Crystal Oscillator, which can be bypassed
• One Fast RC Oscillator, factory programmed. Three output frequencies can be selected: 4, 8
• One 80 to 240 MHz PLL (PLLB) providing a clock for the USB Full Speed Controller
• One 80 to 240 MHz programmable PLL (PLLA), provides the clock, MCK to the processor
or 12 MHz. By default 4 MHz is selected.
and peripherals. The PLLA input frequency is from 3 MHz to 32 MHz.
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