ATmega1281R231 Atmel Corporation, ATmega1281R231 Datasheet - Page 43

• Manufacturer Part Number: ATmega1281R231
• Manufacturer: Atmel Corporation

Specifications of ATmega1281R231

• Flash (kbytes): 128 Kbytes
• Max. Operating Frequency: 16 MHz
• Max I/o Pins: 54
• Spi: 3
• Twi (i2c): 1
• Uart: 2
• Adc Channels: 8
• Adc Resolution (bits): 10
• Adc Speed (ksps): 15
• Analog Comparators: 1
• Crypto Engine: AES
• Sram (kbytes): 8
• Eeprom (bytes): 4096
• Operating Voltage (vcc): 1.8 to 3.6
• Timers: 6
• Frequency Band: 2.4 GHz
• Max Data Rate (mb/s): 2
• Antenna Diversity: Yes
• External Pa Control: Yes
• Power Output (dbm): 3
• Receiver Sensitivity (dbm): -101
• Receive Current Consumption (ma): 13.2
• Transmit Current Consumption (ma): 14.4
• Link Budget (dbm): 104

2549N–AVR–05/11
C1 and C2 should always be equal for both crystals and resonators. The optimal value of the
capacitors depends on the crystal or resonator in use, the amount of stray capacitance, and the
electromagnetic noise of the environment. Some initial guidelines for choosing capacitors for
use with crystals are given in
the manufacturer should be used.
Figure 10-2. Crystal Oscillator Connections
The Low Power Oscillator can operate in three different modes, each optimized for a specific fre-
quency range. The operating mode is selected by the fuses CKSEL3:1 as shown in
Table 10-3.
Notes:
The CKSEL0 Fuse together with the SUT1:0 Fuses select the start-up times as shown in
10-4.
Table 10-4.
Ceramic resonator, slowly
Ceramic resonator, BOD
Frequency Range (MHz)
Ceramic resonator, fast
Oscillator Source /
Power Conditions
rising power
rising power
1. This is the recommended CKSEL settings for the different frequency ranges.
2. This option should not be used with crystals, only with ceramic resonators.
3. If 8MHz frequency exceeds the specification of the device (depends on V
4. Maximum frequency when using ceramic oscillator is 10MHz.
8.0 - 16.0
enabled
0.4 - 0.9
0.9 - 3.0
3.0 - 8.0
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.
Low Power Crystal Oscillator Operating Modes
Start-up Times for the Low Power Crystal Oscillator Clock Selection
(4)
CKSEL3:1
Start-up Time from
Table
Power-down and
100
ATmega640/1280/1281/2560/2561
Power-save
101
110
111
258 CK
258 CK
1K CK
(2)
10-3. For ceramic resonators, the capacitor values given by
C2
C1
(1)
Recommended Range for Capacitors C1 and C2 (pF)
Additional Delay
14CK + 4.1ms
14CK + 65ms
(V
from Reset
XTAL2
XTAL1
GND
CC
14CK
= 5.0V)
(3)
(2)
12 - 22
12 - 22
12 - 22
(1)
(1)
–
CKSEL0
CC
0
0
0
), the CKDIV8
Table
SUT1:0
00
01
10
10-3.
Table
43