Datasheet

SAM3X / SAM3A [DATASHEET]
Atmel-11057C-ATARM-SAM3X-SAM3A-Datasheet_23-Mar-15
520
27.3 Block Diagram
Figure 27-1. Clock Generator Block Diagram
27.4 Slow Clock
The Supply Controller embeds a slow clock generator that is supplied with the VDDBU power supply. As soon as
the VDDBU is supplied, both the crystal oscillator and the embedded RC oscillator are powered up, but only the
embedded RC oscillator is enabled. This allows the slow clock to be valid in a short time (about 100 µs).
The Slow Clock is generated either by the Slow Clock Crystal Oscillator or by the Slow Clock RC Oscillator.
The selection between the RC or the crystal oscillator is made by writing the XTALSEL bit in the Supply Controller
Control Register (SUPC_CR).
Power
Management
Controller
Main Clock
MAINCK
PLLA Clock
PLLACK
ControlStatus
3-20 MHz
Crystal
Oscillator
MOSCSEL
Clock Generator
PLLA and
Divider
Embedded
12/8/4 MHz
Fast
RC Oscillator
XIN
XOUT
XIN32
XOUT32
Slow Clock
SLCK
XTALSEL
(Supply Controller)
Embedded
32 kHz RC
Oscillator
32768 Hz
Crystal
Oscillator
UPLL Clock
UPLLCK
USB UTMI
PLL
0
1
0
1