ATSAM3S ATMEL [ATMEL Corporation], ATSAM3S Datasheet - Page 38

• Manufacturer Part Number: ATSAM3S
• Description: AT91 ARM Cortex M3-based Processor
• Manufacturer: ATMEL [ATMEL Corporation]

10.5
38
Clock Generator
SAM3S Summary
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 32768Hz 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, 3 output frequencies can be selected: 4, 8 or 12
• One 60 to 130 MHz PLL (PLLB) providing a clock for the USB Full Speed Controller
• One 60 to 130 MHz programmable PLL (PLLA), capable to provide the clock MCK to the
MHz. By default 4 MHz is selected.
processor and to the peripherals. The input frequency of PLLA is from 7.5 and 20 MHz.
6500AS–ATARM–11-Dec-09