SAM3S1B Atmel Corporation, SAM3S1B Datasheet - Page 425

• Manufacturer Part Number: SAM3S1B
• Manufacturer: Atmel Corporation

Specifications of SAM3S1B

• Flash (kbytes): 64 Kbytes
• Pin Count: 64
• Max. Operating Frequency: 64 MHz
• Cpu: Cortex-M3
• # Of Touch Channels: 23
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 34
• Ext Interrupts: 34
• Usb Transceiver: 1
• Quadrature Decoder Channels: 1
• Usb Speed: Full Speed
• Usb Interface: Device
• Spi: 3
• Twi (i2c): 2
• Uart: 4
• Ssc: 1
• Sd / Emmc: 1
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 10
• Adc Resolution (bits): 12
• Adc Speed (ksps): 1000
• Analog Comparators: 1
• Resistive Touch Screen: No
• Dac Channels: 2
• Dac Resolution (bits): 12
• Temp. Sensor: Yes
• Crypto Engine: No
• Sram (kbytes): 16
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: Yes
• Picopower: No
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 1.8/3.3
• Operating Voltage (vcc): 1.62 to 3.6
• Fpu: No
• Mpu / Mmu: Yes / No
• Timers: 3
• Output Compare Channels: 3
• Input Capture Channels: 3
• Pwm Channels: 4
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

25.5.1
25.5.2
6500C–ATARM–8-Feb-11
4/8/12 MHz Fast RC Oscillator
4/8/12 MHz Fast RC Oscillator Clock Frequency Adjustment
After reset, the 4/8/12 MHz Fast RC Oscillator is enabled with the 4 MHz frequency selected and
it is selected as the source of MAINCK. MAINCK is the default clock selected to start up the
system.
The Fast RC Oscillator 8 and 12 MHz frequencies are calibrated in production. Note that is not
the case for the 4 MHz frequency.
Please refer to the “DC Characteristics” section of the product datasheet.
The software can disable or enable the 4/8/12 MHz Fast RC Oscillator with the MOSCRCEN bit
in the Clock Generator Main Oscillator Register (CKGR_MOR).
The user can also select the output frequency of the Fast RC Oscillator: either 4 MHz, 8 MHz or
12 MHz are available. It can be done through MOSCRCF bits in CKGR_MOR. When changing
this frequency selection, the MOSCRCS bit in the Power Management Controller Status Regis-
ter (PMC_SR) is automatically cleared and MAINCK is stopped until the oscillator is stabilized.
Once the oscillator is stabilized, MAINCK restarts and MOSCRCS is set.
When disabling the Main Clock by clearing the MOSCRCEN bit in CKGR_MOR, the MOSCRCS
bit in the Power Management Controller Status Register (PMC_SR) is automatically cleared,
indicating the Main Clock is off.
Setting the MOSCRCS bit in the Power Management Controller Interrupt Enable Register
(PMC_IER) can trigger an interrupt to the processor.
It is recommended to disable the Main Clock as soon as the processor no longer uses it and
runs out of SLCK, PLLACK or PLLBCK.
The CAL4, CAL8 and CAL12 values in the PMC_OCR registers are the default values set by
Atmel during production. These values are stored in a specific Flash memory area different from
the main memory plane. These values cannot be modified by the user and cannot be erased by
a Flash erase command or by the ERASE pin. Values written by the user's application in the
PMC_OCR register are reset after each power up or peripheral reset.
It is possible for the user to adjust the main RC oscillator frequency through PMC_OCR register.
By default, SEL4/8/12 are low, so the RC oscillator will be driven with Flash calibration bits which
are programmed during chip production.
The user can adjust the trimming of the 4/8/12 MHz Fast RC oscillator through this register in
order to obtain more accurate frequency (to compensate derating factors such as temperature
and voltage).
In order to calibrate the 4 MHz oscillator frequency, SEL4 must be set to 1 and a good frequency
value must be configured in CAL4. Likewise, SEL8/12 must be set to 1 and a trim value must be
configured in CAL8/12 in order to adjust the 8/12 MHz frequency oscillator.
However, the adjustment can not be done to the frequency from which the oscillator is operating.
For example, while running from a frequency of 8 MHz, the user can adjust the 4 and 12 MHz
frequency but not the 8 MHz.
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