ATmega1281 Atmel Corporation, ATmega1281 Datasheet - Page 47

• Manufacturer Part Number: ATmega1281
• Manufacturer: Atmel Corporation

Specifications of ATmega1281

• Flash (kbytes): 128 Kbytes
• Pin Count: 64
• Max. Operating Frequency: 16 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: 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): 8
• Eeprom (bytes): 4096
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: No
• 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: 6
• Output Compare Channels: 16
• Input Capture Channels: 2
• Pwm Channels: 8
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

10.8
2549N–AVR–05/11
128 kHz Internal Oscillator
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 31-1 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 10-9.
Notes:
When this Oscillator is selected, start-up times are determined by the SUT Fuses as shown in
Table
Table 10-10. Start-up times for the internal calibrated RC Oscillator clock selection
Note:
The 128kHz internal Oscillator is a low power Oscillator providing a clock of 128kHz. The fre-
quency is nominal at 3V and 25°C. This clock may be select as the system clock by
programming the CKSEL Fuses to “11” as shown in
Table 10-11. 128kHz Internal Oscillator Operating Modes
Note:
Slowly rising power
Power Conditions
Fast rising power
50, it is possible to get a higher calibration accuracy than by using the factory calibration.
10-9. If selected, it will operate with no external components. During reset, hardware loads
10-10.
BOD enabled
1. The device is shipped with this option selected.
2. If 8MHz frequency exceeds the specification of the device (depends on V
1. The device is shipped with this option selected.
1. Note that the 128kHz oscillator is a very low power clock source, and is not designed for high
Fuse can be programmed in order to divide the internal frequency by 8.
accuracy.
Internal Calibrated RC Oscillator Operating Modes
Frequency Range (MHz)
Nominal Frequency
371.
7.3 - 8.1
128kHz
Start-up Time from Power-
“Calibration Byte” on page
down and Power-save
ATmega640/1280/1281/2560/2561
Reserved
6CK
6CK
6CK
“OSCCAL – Oscillator Calibration Register” on
Table
338.
10-11.
(1)
Additional Delay from
Table 31-1 on page
Reset (V
14CK + 65ms
(1)(2)
14CK + 4.1ms
14CK
CC
CKSEL3:0
CKSEL3:0
= 5.0V)
0010
0011
CC
(1)
), the CKDIV8
371.
SUT1:0
00
01
10
11
47