SAM3N00A Atmel Corporation, SAM3N00A Datasheet - Page 336

• Manufacturer Part Number: SAM3N00A
• Manufacturer: Atmel Corporation

23.5
336
Main Clock
SAM3N
the XIN32 pin are given in the product electrical characteristics section. In order to set the
bypass mode, the OSCBYPASS bit of the Supply Controller Mode Register (SUPC_MR) needs
to be set at 1.
The user can set the Slow Clock Crystal Oscillator in bypass mode instead of connecting a crys-
tal. In this case, the user has to provide the external clock signal on XIN32. The input
characteristics of the XIN32 pin under these conditions are given in the product electrical char-
acteristics section.
The programmer has to be sure to set the OSCBYPASS bit in the Supply Controller Mode Reg-
ister (SUPC_MR) and XTALSEL bit in the Supply Controller Control Register (SUPC_CR).
Figure 23-3
Figure 23-3. Main Clock Block Diagram
The Main Clock has two sources:
• 4/8/12 MHz Fast RC Oscillator which starts very quickly and is used at startup
• 3 to 20 MHz Crystal or Ceramic Resonator-based Oscillator which can be bypassed
Slow Clock
shows the Main Clock block diagram.
XOUT
SLCK
XIN
MOSCRCEN
MOSCRCEN
Ceramic Resonator
MOSCXTCNT
Main Clock
MOSCXTEN
4/8/12 MHz
MOSCXTEN
Frequency
3-20 MHz
Oscillator
Oscillator
3-20 MHz
Oscillator
Fast RC
Counter
Counter
Crystal
or
MOSCRCF
MOSCSEL
MAINRDY
MOSCRCS
MOSCXTS
MOSCSEL
MAINF
1
0
Main Clock
MOSCSELS
MAINCK
11011A–ATARM–04-Oct-10