AT90PWM2B-16SE ATMEL [ATMEL Corporation], AT90PWM2B-16SE Datasheet - Page 238

• Manufacturer Part Number: AT90PWM2B-16SE
• Description: 8-bit Microcontroller with 8K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

21.5
238
Changing Channel or Reference Selection
AT90PWM2/3/2B/3B
Figure 21-6. ADC Timing Diagram, Auto Triggered Conversion
Figure 21-7. ADC Timing Diagram, Free Running Conversion
Table 21-1.
The MUXn and REFS1:0 bits in the ADMUX Register are single buffered through a temporary
register to which the CPU has random access. This ensures that the channels 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 conversion starts, the
channel and reference selection is locked to ensure a sufficient sampling time for the ADC. Con-
tinuous updating resumes in the last ADC clock cycle before the conversion completes (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.
Condition
Sample & Hold
(Cycles from Start of Conversion)
Conversion Time
(Cycles)
Cycle Number
ADC Clock
Trigger
Source
ADATE
ADIF
ADCH
ADCL
ADC Conversion Time
Prescaler
Reset
MUX and REFS
Update
1
Cycle Number
ADC Clock
ADSC
ADIF
ADCH
ADCL
2
First Conversion
3
Conversion
Complete
One Conversion
4
14
13.5
25
5
15
Sample &
Hold
6
16
7
Next Conversion
1
One Conversion
Sign and MSB of Result
LSB of Result
8
2
MUX and REFS
Update
Single Ended
3
Conversion,
Normal
Sample & Hold
13
Conversion
4
Complete
15.5
3.5
14
5
15
16
Sign and MSB of Result
Auto Triggered
LSB of Result
Conversion
Next Conversion
4317J–AVR–08/10
1
Prescaler
Reset
16
4
2