Datasheet

150
ATtiny828 [DATASHEET]
8371A–AVR–08/12
Notes: 1. After switching to internal voltage reference the ADC requires a settling time of 1ms before measurements
are stable. Conversions starting before this may not be reliable. The ADC must be enabled during the set-
tling time.
2. See “Temperature Measurement” on page 148.
If these bits are changed during a conversion, the change will not go into effect until the conversion is complete (ADIF in
ADCSRA is set).
15.13.2 ADMUXB – ADC Multiplexer Selection Register
z Bits 7, 6, 2, 1 – Res: Reserved Bits
These bits are reserved and will always read zero.
z Bit 5 – REFS: Reference Selection Bit
This bits selects the voltage reference for the ADC, as shown in Table 52.
Table 52. Voltage Reference Selections for ADC
If this bit is changed during a conversion, the change will not go in effect until this conversion is complete (ADIF in
ADCSR is set).
011000 ADC24 PD0
011001 ADC25 PD1
011010 ADC26 PD2
011011 ADC27 PD3
011100 Ground GND
011101 Internal 1.1V reference
(1)
(internal)
011110 Temperature sensor
(2)
(internal)
011111 Supply voltage VCC
100000 – 111111 Reserved (not connected)
MUX[5:0] Single Ended Input Pin
Bit 76543210
(0x7D) ––REFS
– – – – MUX5 ADMUXB
Read/Write R R R/W R R R R R/W
Initial Value 0 0 0 0 0 0 0 0
REFS Voltage Reference Selection
0 V
CC
used as analog reference
1 Internal 1.1V voltage reference