atmega32c1 ATMEL Corporation, atmega32c1 Datasheet - Page 232

• Manufacturer Part Number: atmega32c1
• Description: Atmega32m1 Automotive 8-bit Avr Microcontroller With 32k/64k Bytes In-system Programmable Flash
• Manufacturer: ATMEL Corporation

18.5
232
Changing Channel or Reference Selection
ATmega32/64/M1/C1
Figure 18-6. ADC Timing Diagram, Auto Triggered Conversion
Figure 18-7. ADC Timing Diagram, Free Running Conversion
Table 18-1.
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 eight ADC clock cycle before the conversion completes
(ADIF in ADCSRA is set). Note that the conversion starts on the second following rising CPU
clock edge after ADSC is written. The user is thus advised not to write new channel or reference
selection values to ADMUX until two 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
2
3
4
First Conversion
5
Sample &
Hold
6
13.5
7
25
One Conversion
8
Cycle Number
ADC Clock
ADSC
ADIF
ADCH
ADCL
Conversion
11
Conversion
Complete
Complete
One Conversion
12
12
Single Ended
Conversion,
13
13
Normal
15.5
14
3.5
14
Sign and MSB of Result
Next Conversion
1
Sign and MSB of Result
LSB of Result
LSB of Result
Next Conversion
2
MUX and REFS
Update
1
Prescaler
Reset
3
2
Auto Triggered
Sample & Hold
Conversion
4
7647A–AVR–02/08
5
16
2