Atmel ARM-Based Evaluation Kit for SAM4S16C, 32-Bit ARM® Cortex® Microcontroller ATSAM4S-WPIR-RD ATSAM4S-WPIR-RD Data Sheet
Product codes
ATSAM4S-WPIR-RD
499
SAM4S Series [DATASHEET]
Atmel-11100G-ATARM-SAM4S-Datasheet_27-May-14
28.3
Block Diagram
Figure 28-1.
Clock Generator Block Diagram
28.4
Slow Clock
The Supply Controller embeds a slow clock generator that is supplied with the VDDIO power supply. As soon as
the VDDIO 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
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).
28.4.1 Slow Clock RC Oscillator
By default, the slow clock RC oscillator is enabled and selected. The user has to take into account the possible
drifts of the RC oscillator. More details are given in the section “DC Characteristics” of the product datasheet.
PLLA and
Divider /2
Divider /2
PLLB and
Divider /2
PLLADIV2
PLLBDIV2
Management
Controller
MAINCK
Control
Status
MOSCSEL
XIN
XOUT
XIN32
XOUT32
SLCK
(Supply Controller)
PLLBCK
0
1
0
1
3-20 MHz
Crystal
or
Ceramic
Resonator
Oscillator
Embedded
4/8/12 MHz
Fast
RC Oscillator
32768 Hz
Crystal
Oscillator
Embedded
32 kHz
RC Oscillator
Clock Generator
XTALSEL
Slow Clock
Main Clock
PLLB Clock
PLLA Clock
PLLACK
Power
PMC_MCKR
PMC_MCKR
CKGR_MOR