ATSAM3U-EK Atmel, ATSAM3U-EK Datasheet - Page 460

• 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

27.6
UTMI Phase Lock Loop Programming
The clock source of the UTMI PLL is the 3-20 MHz Crystal Oscillator. When the 4/8/12 MHz Fast
RC Oscillator is selected as the source of MAINCK, the 12 MHz frequency must also be selected
because the UTMI PLL multiplier contains a built-in multiplier of x 40 to obtain the USB High
Speed 480 MHz.
A 12 MHz crystal is needed to use the USB.
Figure 27-5. UTMI PLL Block Diagram
UPLLEN
3-20 MHz Crystal
UTMI PLL
UPLLCK
UPLLCOUNT
UTMI PLL
SLCK
LOCKU
Counter
Whenever the UTMI PLL is enabled by writing UPLLEN in CKGR_UCKR, the LOCKU bit in
PMC_SR is automatically cleared. The values written in the PLLCOUNT field in CKGR_UCKR
are loaded in the UTMI PLL counter. The UTMI PLL counter then decrements at the speed of
the Slow Clock divided by 8 until it reaches 0. At this time, the LOCKU bit is set in PMC_SR and
can trigger an interrupt to the processor. The user has to load the number of Slow Clock cycles
required to cover the UTMI PLL transient time into the PLLCOUNT field.
SAM3U Series
460
6430D–ATARM–25-Mar-11