ATmega644P Atmel Corporation, ATmega644P Datasheet - Page 36

• Manufacturer Part Number: ATmega644P
• Manufacturer: Atmel Corporation

Specifications of ATmega644P

• Flash (kbytes): 64 Kbytes
• Pin Count: 44
• Max. Operating Frequency: 20 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 16
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 32
• Ext Interrupts: 32
• Usb Speed: No
• Usb Interface: No
• Spi: 3
• Twi (i2c): 1
• Uart: 2
• 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): 4
• Eeprom (bytes): 2048
• 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: 6
• Input Capture Channels: 1
• Pwm Channels: 6
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

6.6
8011O–AVR–07/10
Calibrated Internal RC Oscillator
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 the user. See
25-4 on page 330
The device is shipped with the CKDIV8 Fuse programmed. See
page 38
This clock may be selected as the system clock by programming the CKSEL Fuses as shown in
Table
the pre-programmed calibration value into the OSCCAL Register and thereby automatically cal-
ibrates the RC Oscillator. The accuracy of this calibration is shown as Factory calibration in
Table 25-4 on page
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 6-10.
Notes:
When this Oscillator is selected, start-up times are determined by the SUT Fuses as shown in
Table 6-11 on page
Table 6-11.
Note:
Power Conditions
BOD enabled
Fast rising power
Slowly rising power
40, it is possible to get a higher calibration accuracy than by using the factory calibration.
6-10. If selected, it will operate with no external components. During reset, hardware loads
1. The device is shipped with this option selected.
2. If 8 MHz frequency exceeds the specification of the device (depends on V
1.
for more details.
The device is shipped with this option selected.
Fuse can be programmed in order to divide the internal frequency by 8.
Internal Calibrated RC Oscillator Operating Modes
Start-up times for the Internal Calibrated RC Oscillator clock selection
Frequency Range
and
330.
36.
”Internal Oscillator Speed” on page 356
7.3 - 8.1
Start-up Time from Power-
”Calibration Byte” on page
down and Power-save
(2)
(MHz)
Reserved
6 CK
6 CK
6 CK
ATmega164P/324P/644P
”OSCCAL – Oscillator Calibration Register” on
296.
Additional Delay from
Reset (V
Table 25-4 on page
and
14CK + 4.1 ms
14CK + 65 ms
”System Clock Prescaler” on
page 380
14CK
CC
CKSEL3..0
= 5.0V)
0010
CC
(1)
for more details.
), the CKDIV8
330.
SUT1..0
10
00
01
11
Table
(1)
36