16.3.3 Alternate Functions of Port C

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

Table 16-9. Port C Pins Alternate Functions
Port PinAlternate Function
PC7

TOSC2 (Timer Oscillator pin 2)

PCINT23 (Pin Change Interrupt 23)

PC6

TOSC1 (Timer Oscillator pin 1)

PCINT22 (Pin Change Interrupt 22)

PC5

ACO

TDI (JTAG Test Data Input)

PCINT21 (Pin Change Interrupt 21)

PC4

OC4A (Timer/Counter 4 Output Compare Match A Output)

TDO (JTAG Test Data Output)

PCINT20 (Pin Change Interrupt 20)

PC3

ICP4 (Timer/Counter4 Input Capture Trigger)

TMS (JTAG Test Mode Select)

PCINT19 (Pin Change Interrupt 19)

PC2

T4 (Timer/Counter 4 External Counter Input)

TCK (JTAG Test Clock)

PCINT18 (Pin Change Interrupt 18)

PC1

SDA0 (two-wire Serial Bus0 Data Input/Output Line)

PCINT17 (Pin Change Interrupt 17)

PC0

SCL0 (two-wire Serial Bus0 Clock Line)

PCINT16 (Pin Change Interrupt 16)

The alternate pin configuration is as follows:
  • TOSC2/PCINT23 – Port C, Bit 7
    • TOSC2, Timer Oscillator pin 2. The PC7 pin can serve as an external interrupt source to the MCU.
    • PCINT23: Pin Change Interrupt source 23. The PC7 pin can serve as an external interrupt source.
  • TOSC1/PCINT22 – Port C, Bit 6
    • TOSC1, Timer Oscillator pin 1. The PC6 pin can serve as an external interrupt source to the MCU.
    • PCINT22: Pin Change Interrupt source 22. The PC6 pin can serve as an external interrupt source.
  • TDI/PCINT21 – Port C, Bit 5
    • TDI: JTAG Test Data Input
    • PCINT21: Pin Change Interrupt source 21. The PC5 pin can serve as an external interrupt source.
  • OC4A/TDO/PCINT20 – Port C, Bit 4
    • OC4A: Timer/Counter 4 Output Compare Match A Output
    • TDO: JTAG Test Data Output
    • PCINT20: Pin Change Interrupt source 20. The PC4 pin can serve as an external interrupt source.
  • TMS/ICP4/PCINT19 – Port C, Bit 3
    • TMS: JTAG Test Mode Select
    • ICP4: Timer/Counter4 Input Capture Trigger
    • PCINT19: Pin Change Interrupt source 19. The PC3 pin can serve as an external interrupt source.
  • TCK/T4/PCINT18 – Port C, Bit 2
    • TCK: JTAG Test Clock
    • T4: Timer/Counter 4 External Counter Input
    • PCINT18: Pin Change Interrupt source 18. The PC2 pin can serve as an external interrupt source.
  • SDA0/PCINT17 – Port C, Bit 1
    • SDA0: two-wire Serial Bus0 Data Input/Output Line
    • PCINT17: Pin Change Interrupt source 17. The PC1 pin can serve as an external interrupt source.
  • SCL0/PCINT16 – Port C, Bit 0
    • SCL0: two-wire Serial Bus0 Clock Line
    • PCINT16: Pin Change Interrupt source 16. 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 16-5.

Table 16-10. Overriding Signals for Alternate Functions in PC7...PC4
Signal
NamePC7/TOSC2/PCINT23PC6/TOSC1/PCINT22PC5/TDI/PCINT21PC4/OC4A/TDO/PCINT20
PUOEAS2 • EXCLKAS2JTAGENJTAGEN
PUOV0011
DDOEAS2 • EXCLKAS2JTAGEN

JTAGEN
OC4A ENABLE

DDOV000

SHIFT_IR + SHIFT_DR + OC4A

PVOE000JTAGEN
PVOV000TDO
DIEOEAS2 • EXCLK + PCINT23 • PCIE2AS2 + PCINT22 • PCIE2JTAGEN + PCINT21 • PCIE2JTAGEN + PCINT20 • PCIE2
DIEOVAS2EXCLK + AS2JTAGENJTAGEN
DIPCINT23 INPUTPCINT22 INPUTPCINT21 INPUTPCINT20 INPUT
AIOT/C2 OSC OUTPUTT/C1 OSC INPUTTDI INPUT-
Table 16-11. Overriding Signals for Alternate Functions in PC3...PC0
Signal
NamePC3/TMS/ICP4/PCINT19PC2/T4/PCINT18PC1/SDA0/PCINT17PC0/SCL0/PCINT16
PUOEJTAGENJTAGENTWENTWEN
PUOV11PORTC1 • PUDPORTC0 • PUD
DDOEJTAGENJTAGENTWENTWEN
DDOV0000
PVOE00TWENTWEN
PVOV00SDA OUTSCL OUT
DIEOEJTAGEN + PCINT19 • PCIE2JTAGEN + PCINT18 • PCIE2PCINT17 • PCIE2PCINT16 • PCIE2
DIEOVJTAGENJTAGEN11
DI

ICP4 INPUT
PCINT19 INPUT

T4 INPUT
PCINT18 INPUT

PCINT17 INPUTPCINT16 INPUT
AIOTMS INPUTTCK INPUTSDA0 INPUTSCL0 INPUT