ATtiny261 Atmel Corporation, ATtiny261 Datasheet - Page 148

• Manufacturer Part Number: ATtiny261
• Manufacturer: Atmel Corporation

Specifications of ATtiny261

• Flash (kbytes): 2 Kbytes
• Pin Count: 20
• Max. Operating Frequency: 20 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 4
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 16
• Ext Interrupts: 16
• Usb Speed: No
• Usb Interface: No
• Spi: 1
• Twi (i2c): 1
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 11
• Adc Resolution (bits): 10
• Adc Speed (ksps): 15
• Analog Comparators: 1
• Resistive Touch Screen: No
• Temp. Sensor: Yes
• Crypto Engine: No
• Sram (kbytes): 0.12
• Eeprom (bytes): 128
• 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: 2
• Output Compare Channels: 6
• Input Capture Channels: 1
• Pwm Channels: 6
• 32khz Rtc: No
• Calibrated Rc Oscillator: Yes

15.6
148
Changing Channel or Reference Selection
ATtiny261/461/861
Figure 15-7. ADC Timing Diagram, Free Running Conversion
For a summary of conversion times, see
Table 15-1.
The MUX5:0 and REFS2:0 bits in the ADCSRB and ADMUX registers are single buffered
through a temporary register to which the CPU has random access. This ensures that the chan-
nels and reference selection only takes place at a safe point during the conversion. The channel
and reference selection is continuously updated until a conversion is started. Once the conver-
sion starts, the channel and reference selection is locked to ensure a sufficient sampling time for
the ADC. Continuous updating resumes in the last ADC clock cycle before the conversion com-
pletes (ADIF in ADCSRA is set). Note that the conversion starts on the following rising ADC
clock edge after ADSC is written. The user is thus advised not to write new channel or reference
selection values to ADMUX until one ADC clock cycle after ADSC is written.
If Auto Triggering is used, the exact time of the triggering event can be indeterministic. Special
care must be taken when updating the ADMUX Register, in order to control which conversion
will be affected by the new settings.
If both ADATE and ADEN is written to one, an interrupt event can occur at any time. If the
ADMUX Register is changed in this period, the user cannot tell if the next conversion is based
on the old or the new settings.
ADMUX can be safely updated in the following ways:
Condition
First conversion
Normal conversions
Auto Triggered conversions
ADC Conversion Time
Cycle Number
ADC Clock
ADSC
ADIF
ADCH
ADCL
Conversion
Sample & Hold
(Cycles from Start of Conversion)
Complete
One Conversion
11
12
Table
13.5
1.5
13
2
15-1.
Next Conversion
1
Sign and MSB of Result
LSB of Result
2
MUX and REFS
Update
3
Sample & Hold
Total Conversion Time (Cycles)
4
13.5
25
13
2588E–AVR–08/10