97
ATtiny26(L)
1477B–AVR–04/02
Alternate Functions of Port A Port A has an alternate functions as analog inputs for the ADC and Analog Comparator
and pin change interrupt as shown in Table 41. If some Port A pins are configured as
outputs, it is essential that these do not switch when a conversion is in progress. This
might corrupt the result of the conversion. The ADC is described in “Analog to Digital
Converter” on page 77. Analog Comparator is described in “Analog Comparator” on
page 74. Pin change interrupt triggers on pins PA7, PA6 and PA3 if interrupt is enabled
and it is not masked by the alternate functions even if the pin is configured as an output.
See details from “Pin Change Interrupt” on page 38.
Table 42 and Table 43 relates the alternate functions of Port A to the overriding signals
shown in Figure 57 on page 95. Thera are changes on PA7, PA6, and PA3 digital
inputs. PA3 output and pullup driver are also overridden.
• ADC6/AIN1 Port – A, Bit 7
AIN1: Analog Comparator Negative input and ADC6: ADC input channel 6
. Configure
the port pin as input with the internal pull-up switched off to avoid the digital port function
from interfering with the function of the analog comparator or analog to digital converter.
PCINT1: Pin Change Interrupt 1 pin. Pin change interrupt is enabled on pin when global
interrupt is enabled, pin change interrupt is enabled and the alternate function do not
mask the interrupt. The masking alternate function is the Analog Comparator. Digital
input is enabled on pin PA7 also in SLEEP modes, if the pin change interrupt is enabled
and not masked by the alternate function.
• ADC5/AIN0 Port – A, Bit 6
AIN0: Analog Comparator Positive input and ADC5: ADC input channel 5
. Configure the
port pin as input with the internal pull-up switched off to avoid the digital port function
from interfering with the function of the Analog Comparator or analog to digital
converter.
PCINT1: Pin Change Interrupt 1 pin. Pin change interrupt is enabled on pin when global
interrupt is enabled, pin change interrupt is enabled and the alternate function do not
mask the interrupt. The masking alternate function is the Analog Comparator. Digital
input is enabled on pin PA6 also in SLEEP modes, if the pin change interrupt is enabled
and not masked by the alternate function.
Table 41. Port A Pins Alternate Functions
Port Pin Alternate Function
PA7 ADC6 (ADC input channel 6)
AIN1 (Analog Comparator negative input)
PCINT1 (Pin Change Interrupt 1)
PA6 ADC5 (ADC input channel 5)
AIN0 (Analog Comparator positive input)
PCINT1 (Pin Change Interrupt 1)
PA5 ADC4 (ADC input channel 4)
PA4 ADC3 (ADC input channel 3)
PA3 AREF (ADC external reference)
PCINT1 (Pin Change Interrupt 1)
PA2 ADC2 (ADC input channel 2)
PA1 ADC1 (ADC input channel 1)
PA0 ADC0 (ADC input channel 0)
(18 páginas)
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