Datasheet

209
7728G–AVR–06/10
ATtiny87/ATtiny167
17.11.4 ADCSRB – ADC Control and Status Register B
• Bit 7– BIN: Bipolar Input Mode
The gain stage is working in the unipolar mode as default, but the bipolar mode can be
selected by writing the BIN bit in the ADCSRB register. In the unipolar mode only one-sided
conversions are supported and the voltage on the positive input must always be larger than
the voltage on the negative input. Otherwise the result is saturated to the voltage reference. In
the bipolar mode two-sided conversions are supported and the result is represented in the
two’s complement form. In the unipolar mode the resolution is 10 bits and the bipolar mode the
resolution is 9 bits + 1 sign bit.
• Bit 3 – Res: Reserved Bit
This bit is reserved for future use. For compatibility with future devices it must be written to
zero when ADCSRB register is written.
• Bits 2:0 – ADTS2:0: ADC Auto Trigger Source
If ADATE in ADCSRA register is written to one, the value of these bits selects which source
will trigger an ADC conversion. If ADATE is cleared, the ADTS2:0 settings will have no effect.
A conversion will be triggered by the rising edge of the selected Interrupt Flag. Note that
switching from a trigger source that is cleared to a trigger source that is set, will generate a
positive edge on the trigger signal. If ADEN in ADCSRA register is set, this will start a conver-
sion. Switching to Free Running mode (ADTS[2:0]=0) will not cause a trigger event, even if the
ADC Interrupt Flag is set.
17.11.5 DIDR0 – Digital Input Disable Register 0
Bit 76543210
BIN
ACME ACIR1 ACIR0 – ADTS2 ADTS1 ADTS0 ADCSRB
Read/Write R/W R/W R/W R/W R R/W R/W R/W
Initial Value00000000
Table 17-7. ADC Auto Trigger Source Selections
ADTS2 ADTS1 ADTS0 Trigger Source
0 0 0 Free Running mode
0 0 1 Analog Comparator
0 1 0 External Interrupt Request 0
0 1 1 Timer/Counter1 Compare Match A
1 0 0 Timer/Counter1 Overflow
1 0 1 Timer/Counter1 Compare Match B
1 1 0 Timer/Counter1 Capture Event
1 1 1 Watchdog Interrupt Request
Bit 76543210
ADC7D /
AIN1D
ADC6D /
AIN0D
ADC5D ADC4D ADC3D ADC2D ADC1D ADC0D DIDR0
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value00000000