8-bit AVR Microcontroller

I/O Multiplexing

Each pin is by default controlled by the PORT as a general purpose I/O and alternatively it can be assigned to one of the peripheral functions.

The following table describes the peripheral signals multiplexed to the PORT I/O pins.

Table 1. 32-Pin TQFP and MLF: PORT Function Multiplexing
No	PAD32	EXTINT	ADC/AC	OSC	T/C # 0	T/C # 1	USART	I2C	SPI
1	PD[3]	INT1
2	PD[4]				T0		XCK0
3	GND
4	VCC
5	GND
6	VCC
7	PB[6]			XTAL1/TOSC1
8	PB[7]			XTAL2/TOSC2
9	PD[5]					T1
10	PD[6]		AIN0
11	PD[7]		AIN1
12	PB[0]				ICP1
13	PB[1]				OC1A
14	PB[2]				OC1B				SS0
15	PB[3]				OC2				MOSI0
16	PB[4]								MISO0
17	PB[5]								SCK0
18	AVCC
19	ADC6		ADC6
20	AREF
21	GND
22	ADC7		ADC7
23	PC[0]		ADC0
24	PC[1]		ADC1
25	PC[2]		ADC2
26	PC[3]		ADC3
27	PC[4]		ADC4					SDA0
28	PC[5]		ADC5					SCL0
29	PC[6]/RESET
30	PD[0]						RXD0
31	PD[1]						TXD0
32	PD[2]	INT0

Table 2. 28-Pin PDIP: PORT Function Multiplexing
No	PAD28	EXTINT	ADC/AC	OSC	T/C # 0	T/C # 1	USART	I2C	SPI
1	PC[6]/RESET
2	PD[0]						RXD0
3	PD[1]						TXD0
4	PD[2]	INT0
5	PD[3]	INT1
6	PD[4]				T0		XCK0
7	VCC
8	GND
9	PB[6]			XTAL1/TOSC1
10	PB[7]			XTAL2/TOSC2
11	PD[5]					T1
12	PD[6]		AIN0
13	PD[7]		AIN1
14	PB[0]				ICP1
15	PB[1]				OC1A
16	PB[2]				OC1B				SS0
17	PB[3]				OC2				MOSI0
18	PB[4]								MISO0
19	PB[5]								SCK0
20	AVCC
21	AREF
22	GND
23	PC[0]		ADC0
24	PC[1]		ADC1
25	PC[2]		ADC2
26	PC[3]		ADC3
27	PC[4]		ADC4					SDA0
28	PC[5]		ADC5					SCL0