Datasheet

336
11011B–ATARM–21-Feb-12
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).
23.5 Main Clock
Figure 23-3 shows the Main Clock block diagram.
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
XIN
XOUT
MOSCXTEN
MOSCXTCNT
MOSCXTS
Main Clock
Frequency
Counter
MAINF
MAINRDY
SLCK
Slow Clock
3-20 MHz
Crystal
or
Ceramic Resonator
Oscillator
3-20 MHz
Oscillator
Counter
MOSCRCEN
4/8/12 MHz
Fast RC
Oscillator
MOSCRCS
MOSCRCF
MOSCRCEN
MOSCXTEN
MOSCSEL
MOSCSEL
MOSCSELS
1
0
MAINCK
Main Clock