ATSAM3U-EK Atmel, ATSAM3U-EK Datasheet - Page 455

• Manufacturer Part Number: ATSAM3U-EK
• Description: KIT EVAL FOR AT91SAM3U CORTEX
• Manufacturer: Atmel
• Type: MCUr

Specifications of ATSAM3U-EK

• Contents: Board
• Processor To Be Evaluated: SAM3U
• Data Bus Width: 32 bit
• Interface Type: RS-232, USB
• Operating Supply Voltage: 3 V
• Silicon Manufacturer: Atmel
• Core Architecture: ARM
• Core Sub-architecture: Cortex - M3
• Silicon Core Number: SAM3U4E
• Silicon Family Name: SAM3U
• Kit Contents: Board CD Docs
• Rohs Compliant: Yes
• For Use With/related Products: AT91SAM3U
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

27.3
27.3.1
27.3.2
6430D–ATARM–25-Mar-11
Slow Clock
Slow Clock RC Oscillator
Slow Clock Crystal Oscillator
The Slow Clock is generated either by the Slow Clock Crystal Oscillator or by the Slow Clock RC
Oscillator.
The selection is made by writing the XTALSEL bit in the Supply Controller Control Register
(SUPC_CR).
By default, the RC Oscillator is selected.
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 Char-
acteristics” of the product datasheet.
It can be disabled via the XTALSEL bit in the Supply Controller Control Register (SUPC_CR).
The Clock Generator integrates a 32,768 Hz low-power oscillator.The XIN and XOUT pins must
be connected to a 32,768 Hz crystal. Two external capacitors must be wired as shown in
27-2.More details are given in the section “DC Characteristics” of the product datasheet.
Note that the user is not obliged to use the Slow Clock Crystal and can use the RC Oscillator
instead. In this case, XIN and XOUT can be left unconnected.
Figure 27-2. Typical Slow Clock Crystal Oscillator Connection
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 XIN pin under these conditions are given in the product electrical charac-
teristics 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).
XIN32
32,768 Hz
Crystal
XOUT32
GNDBU
SAM3U Series
Figure
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