ATmega325P Atmel Corporation, ATmega325P Datasheet - Page 33

• Manufacturer Part Number: ATmega325P
• Manufacturer: Atmel Corporation

Specifications of ATmega325P

• Flash (kbytes): 32 Kbytes
• Pin Count: 64
• Max. Operating Frequency: 20 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 16
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 54
• Ext Interrupts: 17
• Usb Speed: No
• Usb Interface: No
• Spi: 2
• Twi (i2c): 1
• Uart: 1
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 8
• Adc Resolution (bits): 10
• Adc Speed (ksps): 15
• Analog Comparators: 1
• Resistive Touch Screen: No
• Temp. Sensor: No
• Crypto Engine: No
• Sram (kbytes): 2
• Eeprom (bytes): 1024
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: Yes
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 1.8 to 5.5
• Operating Voltage (vcc): 1.8 to 5.5
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 3
• Output Compare Channels: 4
• Input Capture Channels: 1
• Pwm Channels: 4
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

8.6
8023F–AVR–07/09
Calibrated Internal RC Oscillator
The Low-frequency Crystal Oscillator must be selected by setting the CKSEL Fuses to “0110” or
“0111” as shown in
Table
Table 8-6.
Table 8-7.
Note:
By default, the Internal RC Oscillator provides an approximate 8 MHz clock. Though voltage and
temperature dependent, this clock can be very accurately calibrated by the user. See
on page 307
”System Clock Prescaler” on page 35
This clock may be selected as the system clock by programming the CKSEL Fuses as shown in
Table 8-8 on page
hardware loads the pre-programmed calibration value into the OSCCAL Register and thereby
automatically calibrates the RC Oscillator. The accuracy of this calibration is shown as Factory
calibration in
By changing the OSCCAL register from SW, see
page
The accuracy of this calibration is shown as User calibration in
When this Oscillator is used as the chip clock, the Watchdog Oscillator will still be used for the
Watchdog Timer and for the Reset Time-out. For more information on the pre-programmed cali-
bration value, see the section
Table 8-8.
Notes:
CKSEL3..0
SUT1..0
0110
0111
00
01
10
11
36, it is possible to get a higher calibration accuracy than by using the factory calibration.
8-6.
(1)
1. This option should only be used if frequency stability at start-up is not important for the
1. The device is shipped with this option selected.
2. The frequency ranges are preliminary values. Actual values are TBD.
3. If 8 MHz frequency exceeds the specification of the device (depends on V
application
Fuse can be programmed in order to divide the internal frequency by 8.
Table 26-1 on page
for more details. The device is shipped with the CKDIV8 Fuse programmed. See
Start-up Times for the Low-frequency Crystal Oscillator Clock Selection
Start-up Times for the Low-frequency Crystal Oscillator Clock Selection
Internal Calibrated RC Oscillator Operating Modes
Additional Delay from Reset (V
Frequency Range
33. If selected, it will operate with no external components. During reset,
Power-down and Power-save
Table
Start-up Time from
7.3 - 8.1
8-7. Start-up times are determined by the SUT Fuses as shown in
4 CK + 4.1 ms
4 CK + 65 ms
”Calibration Byte” on page
32K CK
1K CK
4 CK
307.
(2)
(MHz)
for more details.
CC
= 5.0V)
”OSCCAL – Oscillator Calibration Register” on
Reserved
Recommended Usage
Fast rising power or BOD enabled
Slowly rising power
Stable frequency at start-up
Recommended Usage
Stable frequency at start-up
274.
ATmega325P/3250P
Table 26-1 on page
(1)(3)
CKSEL3..0
0010
CC
), the CKDIV8
307.
Table 26-1
33