17.3.2 Alternate Functions of Port C

The Port C pins with alternate functions are shown in the table below:

The alternate pin configuration is as follows:

• RESET/PCINT14 – Port C, Bit 6
  • RESET, Reset pin: When the RSTDISBL Fuse is programmed, this pin functions as a normal I/O pin, and the part will have to rely on Power-on Reset and Brown-out Reset as its reset sources. When the RSTDISBL Fuse is unprogrammed, the reset circuitry is connected to the pin, and the pin cannot be used as an I/O pin.
  • PCINT14: Pin Change Interrupt source 14. The PC6 pin can serve as an external interrupt source.

If PC6 is used as a reset pin, DDC6, PORTC6 and PINC6 will all read 0.

• SCL0/ADC5/PCINT13 – Port C, Bit 5
  • SCL0: Two-wire Serial Interface0 Clock. When the TWEN bit in TWCR0 is set (one) to enable the two-wire Serial Interface, pin PC5 is disconnected from the port and becomes the Serial Clock I/O pin for the two-wire Serial Interface0. In this mode, there is a spike filter on the pin to suppress spikes shorter than 50 ns on the input signal, and the pin is driven by an open drain driver with slew-rate limitation.
  • PCINT13: Pin Change Interrupt source 13. The PC5 pin can serve as an external interrupt source.

  • PC5 can also be used as ADC input Channel 5. The ADC input channel 5 uses digital power.

• SDA0/ADC4/PCINT12 – Port C, Bit 4
  • SDA0: Two-wire Serial Interface0 Data. When the TWEN bit in TWCR0 is set (one) to enable the two-wire Serial Interface, pin PC4 is disconnected from the port and becomes the Serial Data I/O pin for the two-wire Serial Interface0. In this mode, there is a spike filter on the pin to suppress spikes shorter than 50 ns on the input signal, and the pin is driven by an open drain driver with slew-rate limitation.
  • PCINT12: Pin Change Interrupt source 12. The PC4 pin can serve as an external interrupt source.
  • PC4 can also be used as ADC input Channel 4. The ADC input channel 4 uses digital power.

• ADC3/PCINT11 – Port C, Bit 3
  • PC3 can also be used as ADC input Channel 3. The ADC input channel 3 uses analog power.
  • PCINT11: Pin Change Interrupt source 11. The PC3 pin can serve as an external interrupt source.

• ADC2/PCINT10 – Port C, Bit 2
  • PC2 can also be used as ADC input Channel 2. The ADC input channel 2 uses analog power.
  • PCINT10: Pin Change Interrupt source 10. The PC2 pin can serve as an external interrupt source.

• SCK1/ADC1/PCINT9 – Port C, Bit 1

  • PC1 can also be used as ADC input Channel 1. The ADC input channel 1 uses analog power.
  • SCK1: Master Clock output, Slave Clock input pin for SPI1 channel. When the SPI1 is enabled as a Slave, this pin is configured as an input regardless of the setting of DDB5. When the SPI1 is enabled as a Master, the data direction of this pin is controlled by DDC1. When the pin is forced by the SPI1 to be an input, the pull-up can still be controlled by the PORTC1 bit.
  • PCINT9: Pin Change Interrupt source 9. The PC1 pin can serve as an external interrupt source.

• ADC0/MISO1/PCINT8 – Port C, Bit 0
  • PC0 can also be used as ADC input Channel 0. The ADC input channel 0 uses analog power.
  • MISO1: Master1 Data input, Slave Data output pin for SPI1 channel. When the SPI1 is enabled as a Master, this pin is configured as an input regardless of the setting of DDC0. When the SPI1 is enabled as a Slave, the data direction of this pin is controlled by DDC0. When the pin is forced by the SPI1 to be an input, the pull-up can still be controlled by the PORTC0 bit.
  • PCINT8: Pin Change Interrupt source 8. The PC0 pin can serve as an external interrupt source.

The tables below relate the alternate functions of Port C to the overriding signals shown in Figure 17-5.