34
11090BS–ATARM–22-Oct-13
SAM3S8/SD8 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.
10.5 Clock Generator
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. Three output frequencies can be selected: 4, 8
or 12 MHz. By default 4 MHz is selected.
• One 60 to 130 MHz PLL (PLLB) providing a clock for the USB Full Speed Controller
• One 60 to 130 MHz programmable PLL (PLLA), provides the clock, MCK to the processor
and peripherals. The PLLA input frequency is from 3.5 MHz to 20 MHz.
