AT90PWM3 Datasheet, PDF (259/365 Pages) ATMEL Corporation – 8-bit Microcontroller with 8K Bytes In-System Programmable Flash

ADC Control and Status
Register B– ADCSRB
4317B–AVR–02/05
AT90PWM2/3
Set this bit to activate the ADC end of conversion interrupt.
Clear it to disable the ADC end of conversion interrupt.
• Bit 2, 1, 0– ADPS2, ADPS1, ADPS0: ADC Prescaler Selection Bits
These 3 bits determine the division factor between the system clock frequency and input
clock of the ADC.
The different setting are shown in Table 102.
Table 102. ADC Prescaler Selection
ADPS2 ADPS1 ADPS0 Division Factor
0
0
0
2
0
0
1
2
0
1
0
4
0
1
1
8
1
0
0
16
1
0
1
32
1
1
0
64
1
1
1
128
Bit
Read/Write
Initial Value
7
6
ADHSM
-
-
-
0
0
5
4
3
2
1
0
-
ADASCR ADTS3 ADTS2 ADTS1 ADTS0 ADCSRB
-
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
• Bit 7 – ADHSM: ADC High Speed Mode
Writing this bit to one enables the ADC High Speed mode. Set this bit if you wish to
convert with an ADC clock frequency higher than 200KHz.
• Bit 4– ADASCR: Analog to Digital Conversion on Amplified Channel Start
Conversion Request Bit
Set this to request a conversion on an amplified channel.
Cleared by hardware as soon as the Analog to Digital Conversion is started.
Alternatively, this bit can be cleared by writing it to logical zero.
• Bit 3, 2, 1, 0– ADTS3:ADTS0: ADC Auto Trigger Source Selection Bits
These bits are only necessary in case the ADC works in auto trigger mode. It means if
ADATE bit in ADCSRA register is set.
In accordance with the Table 103, these 3 bits select the interrupt event which will gen-
erate the trigger of the start of conversion. The start of conversion will be generated by
the rising edge of the selected interrupt flag whether the interrupt is enabled or not. In
case of trig on PSCnASY event, there is no flag. So in this case a conversion will start
each time the trig event appears and the previous conversion is completed..
Table 103. ADC Auto Trigger Source Selection
ADTS3
ADTS2
ADTS1
ADTS0
0
0
0
0
0
0
0
1
0
0
1
0
Description
Free Running Mode
Analog Comparator 0
External Interrupt Request 0
259