ATSAM3U-EK Atmel, ATSAM3U-EK Datasheet - Page 458

• 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

27.4.4
458
SAM3U Series
Main Clock Frequency Counter
The device features a Main Clock frequency counter that provides the frequency of the Main
Clock.
The Main Clock frequency counter is reset and starts incrementing at the Main Clock speed after
the next rising edge of the Slow Clock in the following cases:
Then, at the 16th falling edge of Slow Clock, the MAINFRDY bit in the Clock Generator Main
Clock Frequency Register (CKGR_MCFR) is set and the counter stops counting. Its value can
be read in the MAINF field of CKGR_MCFR and gives the number of Main Clock cycles during
16 periods of Slow Clock, so that the frequency of the 4/8/12 MHz Fast RC Oscillator or 3 to 20
MHz Crystal Oscillator can be determined.
• when the 4/8/12 MHz Fast RC Oscillator clock is selected as the source of Main Clock and
• when the 3 to 20 MHz Crystal Oscillator is selected as the source of Main Clock and when
• when the Main Clock Oscillator selection is modified
when this oscillator becomes stable (i.e., when the MOSCRCS bit is set)
this oscillator becomes stable (i.e., when the MOSCXTS bit is set)
6430D–ATARM–25-Mar-11