ATmega644P Atmel Corporation, ATmega644P Datasheet - Page 33

• 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

6.4
8011O–AVR–07/10
Full Swing Crystal Oscillator
Table 6-4.
Notes:
This Crystal Oscillator is a full swing oscillator, with rail-to-rail swing on the XTAL2 output. This is
useful for driving other clock inputs and in noisy environments. The current consumption is
higher than the
Oscillator will only operate for Vcc = 2.7 - 5.5 volts.
Some initial guidelines for choosing capacitors for use with crystals are given in
crystal should be connected as described in
The operating mode is selected by the fuses CKSEL3..1 as shown in
Table 6-5.
Notes:
Table 6-6.
Oscillator Source /
Power Conditions
Crystal Oscillator, BOD
enabled
Crystal Oscillator, fast
rising power
Crystal Oscillator, slowly
rising power
Frequency Range
Oscillator Source /
Power Conditions
Ceramic resonator, fast
rising power
Ceramic resonator, slowly
rising power
Ceramic resonator, BOD
enabled
1. These options should only be used when not operating close to the maximum frequency of the
2. These options are intended for use with ceramic resonators and will ensure frequency stability
1. If 8 MHz frequency exceeds the specification of the device (depends on V
device, and only if frequency stability at start-up is not important for the application. These
options are not suitable for crystals.
at start-up. They can also be used with crystals when not operating close to the maximum fre-
quency of the device, and if frequency stability at start-up is not important for the application.
Fuse can be programmed in order to divide the internal frequency by 8. It must be ensured
that the resulting divided clock meets the frequency specification of the device.
0.4 - 20
Start-up Times for the Low Power Crystal Oscillator Clock Selection (Continued)
Full Swing Crystal Oscillator Operating Modes
Start-up Times for the Full Swing Crystal Oscillator Clock Selection
”Low Power Crystal Oscillator” on page
(1)
(MHz)
Start-up Time from
Start-up Time from
Power-down and
Power-down and
Power-save
Power-save
16K CK
16K CK
16K CK
258 CK
258 CK
1K CK
CKSEL3..1
011
”Clock Source Connections” on page
ATmega164P/324P/644P
Additional Delay
Additional Delay
14CK + 4.1 ms
14CK + 65 ms
Recommended Range for Capacitors C1
14CK + 4.1 ms
14CK + 65 ms
(V
(V
from Reset
from Reset
CC
CC
14CK
32. Note that the Full Swing Crystal
14CK
= 5.0V)
= 5.0V)
(2)
(1)
(1)
and C2 (pF)
Table
12 - 22
CKSEL0
CKSEL0
6-5.
CC
0
0
0
1
1
1
), the CKDIV8
Table
31.
SUT1..0
SUT1..0
6-6. The
00
01
10
01
10
11
33