Datasheet

38
6430FS–ATARM–10-Feb-12
SAM3U Series
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 enabling 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 32768 Hz Slow Clock Oscillator with bypass mode
One Low Power RC Oscillator
One 3 to 20 MHz Crystal 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. 8 MHz and 12 MHz output are factory calibrated.
One 480 MHz UPLL providing a clock for the USB High Speed Device Controller. Input
frequency is 12 MHz (only).
One 96 to 192 MHz programmable PLL (PLL A), capable to provide the clock MCK to the
processor and to the peripherals. The input frequency of the PLL A is between 8 and 16 MHz.
Figure 10-2. Clock Generator Block Diagram
Power
Management
Controller
XIN
XOUT
Main Clock
MAINCK
UPLL Clock
UPLLCK
ControlStatus
PLL and
Divider A
PLLA Clock
PLLACK
12M Main
Oscillator
PLL B
On Chip
32k RC OSC
Slow Clock
SLCK
XIN32
XOUT32
Slow Clock
Oscillator
Clock Generator
XTALSEL
HSCK
Divider
/6 /8
On Chip
12/8/4 MHz
RC OSC
MAINSEL