Datasheet

36
11011AS–ATARM–04-Oct-10
SAM3N 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.
9.5 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 or Ceramic resonator Oscillator, which can be bypassed
• One Fast RC Oscillator factory programmed, 3 output frequencies can be selected: 4, 8 or 12
MHz. By default 4 MHz is selected.
• One 60 to 130 MHz programmable PLL, capable to provide the clock MCK to the processor
and to the peripherals. The input frequency of PLL is from 3.5 to 20 MHz.
Figure 9-2. Clock Generator Block Diagram
XIN
XOUT
Main Clock
MAINCK
Slow Clock
SLCK
XIN32
XOUT32
Clock Generator
XTALSEL
MAINSEL
Power
Management
Controller
ControlStatus
PLL and
Divider A
PLLA Clock
PLLACK
3-20 MHz
Main
Oscillator
Slow Clock
Oscillator
On Chip
12/8/4 MHz
RC OSC
On Chip 32 kHz
RC OSC