2 voltage reference for external devices, 3 register description, 1 adcsrb – adc control and status register b – Rainbow Electronics ATmega64M1 User Manual
Page 255
255
8209A–AVR–08/09
ATmega16M1/32M1/64M1
23.2.2
Voltage Reference for External Devices
An external resistor used in conjunction with the Current Source can be used as voltage refer-
ence for external devices. Using a resistor in serie with a lower tolerance than the Current
Source accuracy (
≤
2%) is recommended.
gives an example of voltage references
using standard values of resistors.
23.2.3
Threshold Reference for Internal Analog Comparator
An external resistor used in conjunction with the Current Source can be used as threshold refer-
ence for internal Analog Comparator (
See ”AC – Analog Comparator” on page 256.
). This can
be connected to AIN0 (negative Analog Compare input pin) as well as AIN1 (positive Analog
Compare input pin). Using a resistor in serie with a lower tolerance than the Current Source
accuracy (
≤
2%) is recommended.
gives an example of threshold references using
standard values of resistors.
23.3
Register Description
23.3.1
ADCSRB – ADC Control and Status Register B
• Bit 6 – ISRCEN: Current Source Enable
Set this bit to source a 100µA current to the AREF pin.
Clear this bit to disconnect .
• Bit 5 – AREFEN: Analog Reference pin Enable
Set this bit to connect the internal AREF circuit to the AREF pin.
Clear this bit to disconnect the internal AREF circuit from the AREF pin.
Bit
7
6
5
4
3
2
1
0
ADHSM
ISRCEN
AREFEN
-
ADTS3
ADTS2
ADTS1
ADTS0
ADCSRB
Read/Write
R/W
R/W
R/W
R
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0