ATmega406 Atmel Corporation, ATmega406 Datasheet - Page 30

• Manufacturer Part Number: ATmega406
• Manufacturer: Atmel Corporation

Specifications of ATmega406

• Flash (kbytes): 40 Kbytes
• Pin Count: 48
• Max. Operating Frequency: 1 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 8
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 18
• Ext Interrupts: 4
• Usb Speed: No
• Usb Interface: No
• Twi (i2c): 1
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 11
• Adc Resolution (bits): 12
• Adc Speed (ksps): 1.9
• Resistive Touch Screen: No
• Temp. Sensor: Yes
• Crypto Engine: No
• Sram (kbytes): 2
• Eeprom (bytes): 512
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: No
• Temp. Range (deg C): -30 to 85
• I/o Supply Class: 4.0 to 25
• Operating Voltage (vcc): 4.0 to 25
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 2
• Output Compare Channels: 3
• Pwm Channels: 2
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

30
ATmega406
• Bit 0 - ACS: Asynchronous Clock Select
The ACS bit is used to selected the source of the asynchronous clock for the Coulomb Counter
ADC and Wake-up Timer. The Slow RC Oscillator is selected when this bit is cleared (zero). The
32 kHz Crystal Oscillator is selected when this bit is set (one).
The selected clock source and oscillator enable conditions are illustrated in
Table 7-4.
Recommended algorithm for switching from the RC Oscillator to the Crystal Oscillator as the
asynchronous clock for the Coulomb Counter ADC and Wake-up Timer:
1. Enable the Crystal Oscillator by setting the XOE bit (one).
2. Enable the Wake-up Timer, select a two second timeout, and reset the Wake-up Timer
3. Wait for the Wake-up Timer time-out.
4. Switch to the Crystal Oscillator by setting the ACS bit (one) while keeping the XOE bit set
5. Optional: Wait for another Wake-up Timer time-out, to ensure the Crystal Oscillator is
Recommended algorithm for switching from the Crystal Oscillator to the RC Oscillator as the
asynchronous clock for the Coulomb Counter ADC and Wake-up Timer:
1. Switch to the RC Oscillator by clearing the ACS bit (zero) while keeping the XOE bit set
2. Disable the Crystal Oscillator by clearing the XOE bit (zero) while keeping the ACS bit
Sleep Mode
Power-off or Power-down
Other Sleep Modes
Active Mode
(”Wake-up Timer” on page 49
(one).
operating correctly. This can be done by enabling another timer interrupt with significantly
longer time-out, and checking that the Wake-up Timer time-out occurs first.
(one).
cleared (zero).
Asynchronous Clock Source and Oscillator Enable Conditions
32 kHz Crystal
Oscillator Enable
0
XOE
XOE
for details).
Slow RC
Oscillator Enable
0
ACS & (CADEN | WUTEN)
1
Table
7-4.
2548E–AVR–07/06