19.3.2 Alternate Functions of Port C

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

Table 19-6. Port C Pins Alternate Functions
Port PinAlternate Function
PC6

RESET (Reset pin)

PCINT14 (Pin Change Interrupt 14)

PC5

ADC5 (ADC Input Channel 5)

SCL0 (2-wire Serial Bus Clock Line)

PCINT13 (Pin Change Interrupt 13)

PC4

ADC4 (ADC Input Channel 4)

SDA0 (2-wire Serial Bus Data Input/Output Line)

PCINT12 (Pin Change Interrupt 12)

PC3

ADC3 (ADC Input Channel 3)

PCINT11 (Pin Change Interrupt 11)

PC2

ADC2 (ADC Input Channel 2)

PCINT10 (Pin Change Interrupt 10)

PC1

SCK1 (SPI1 Master Clock output)
ADC1 (ADC Input Channel 1)

PCINT9 (Pin Change Interrupt 9)

PC0

MISO1
ADC0 (ADC Input Channel 0)

PCINT8 (Pin Change Interrupt 8)

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 can not 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: 2-wire Serial Interface0 Clock. When the TWEN bit in TWCR0 is set (one) to enable the 2-wire Serial Interface, pin PC5 is disconnected from the port and becomes the Serial Clock I/O pin for the 2-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: 2-wire Serial Interface0 Data. When the TWEN bit in TWCR0 is set (one) to enable the 2-wire Serial Interface, pin PC4 is disconnected from the port and becomes the Serial Data I/O pin for the 2-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 19-5.

Table 19-7. Overriding Signals for Alternate Functions in PC6...PC4(1)
Signal
NamePC6/RESET/PCINT14PC5/SCL0/ADC5/PCINT13PC4/SDA0/ADC4/PCINT12
PUOERSTDISBLTWEN0TWEN0
PUOV1PORTC5 • PUDPORTC4 • PUD
DDOERSTDISBLTWEN0TWEN0
DDOV0SCL_OUT0SDA_OUT0
PVOE0TWEN0TWEN0
PVOV000
DIEOERSTDISBL + PCINT14 • PCIE1PCINT13 • PCIE1 + ADC5DPCINT12 • PCIE1 + ADC4D
DIEOVRSTDISBLPCINT13 • PCIE1PCINT12 • PCIE1
DIPCINT14 INPUTPCINT13 INPUTPCINT12 INPUT
AIORESET INPUTADC5 INPUT / SCL0 INPUTADC4 INPUT / SDA INPUT0
Note: 1. When enabled, the 2-wire Serial Interface enables slew-rate controls on the output pins PC4 and PC5. This is not shown in the figure. In addition, spike filters are connected between the AIO outputs shown in the port figure and the digital logic of the TWI module.
Table 19-8. Overriding Signals for Alternate Functions in PC3...PC0
Signal
NamePC3/ADC3/
PCINT11PC2/ADC2/
PCINT10PC1/ADC1/SCK1/
PCINT9PC0/ADC0/MISO1/
PCINT8
PUOE00SPE1 • MSTRSPE1 • MSTR
PUOV00PORTC1 • PUDPORTC0 • PUD
DDOE00SPE1 • MSTRSPE1 • MSTR
DDOV0000
PVOE00SPE1 • MSTRSPE1 • MSTR
PVOV00SCK1 OUTPUTSPI1 SLAVE INPUT
DIEOEPCINT11 • PCIE1 +
ADC3DPCINT10 • PCIE1 +
ADC2DPCINT9 • PCIE1 +
ADC1DPCINT8 • PCIE1 +
ADC0D
DIEOVPCINT11 • PCIE1PCINT10 • PCIE1PCINT9 • PCIE1PCINT8 • PCIE1
DIPCINT11 INPUTPCINT10 INPUT

PCINT9 INPUT
SCK1 INPUT

PCINT8 INPUT
SPI1 MASTER INPUT

AIOADC3 INPUTADC2 INPUTADC1 INPUTADC0 INPUT