5.1 I/O Multiplexing


VQFN48/ TQFP48	VQFN32/ TQFP32	SOIC28/SSOP28/ SPDIP28	VQFN28	SOIC20	Pin name^(1,2)	Special	ADCn	ACn	DAC0	ZCDn	USARTn	SPIn	TWIn⁽⁴⁾	TCAn	TCBn	TCD0	EVSYS	CCL-LUTn	ERRCTRL
44	30	22	26	4	PA0	XTALHF1 EXTCLK					0, TxD	0, MOSI⁽³⁾	0, SDA(HC)⁽³⁾	0, WO0				0, IN0
45	31	23	27	5	PA1	XTALHF2					0, RxD	0, MISO⁽³⁾	0, SCL(HC)⁽³⁾	0, WO1				0, IN1
46	32	24	28	6	PA2	TWI Fm+	AIN22				0, XCK 0, TxD⁽³⁾		0, SDA(HC)	0, WO2	0, WO		EVOUTA	0, IN2	HEART
47	1	25	1	7	PA3	TWI Fm+	AIN23				0, XDIR 0, RxD⁽³⁾		0, SCL(HC)	0, WO3	1, WO			0, OUT
48	2	26	2	8	PA4		AIN24				0, TxD⁽³⁾	0, MOSI		0, WO4		WOA			HEART⁽³⁾
1	3	27	3	9	PA5		AIN25				0, RxD⁽³⁾	0, MISO		0, WO5		WOB
2	4	28	4	10	PA6		AIN26				0, XCK⁽³⁾	0, SCK				WOC		0, OUT⁽³⁾	HEART⁽³⁾
3	5	1	5	11	PA7	CLKOUT	AIN27	0, OUT 1, OUT 2, OUT		0, OUT 3, OUT	0, XDIR⁽³⁾	0, SS				WOD	EVOUTA⁽³⁾		HEART⁽³⁾
4	-	-	-	-	PB0						3, TxD			0, WO0⁽³⁾				4, IN0
5	-	-	-	-	PB1						3, RxD			0, WO1⁽³⁾				4, IN1
6	-	-	-	-	PB2						3, XCK		1, SDA(C) 1, SDA(HC)⁽³⁾	0, WO2⁽³⁾			EVOUTB	4, IN2
7	-	-	-	-	PB3						3, XDIR		1, SCL(C) 1, SCL(HC)⁽³⁾	0, WO3⁽³⁾				4, OUT
8	-	-	-	-	PB4						3, TxD⁽³⁾	1, MOSI⁽³⁾		0, WO4⁽³⁾	2, WO⁽³⁾	WOA⁽³⁾
9	-	-	-	-	PB5						3, RxD⁽³⁾	1, MISO⁽³⁾		0, WO5⁽³⁾	3, WO	WOB⁽³⁾
10	6	2	6	-	PC0		AIN28				1, TxD	1, MOSI 0, MOSI⁽³⁾ 0, SCK⁽³⁾		0, WO0⁽³⁾	2, WO			1, IN0
11	7	3	7	12	PC1		AIN29				1, RxD 0, TxD⁽³⁾	1, MISO 0, MISO⁽³⁾ 0, SS⁽³⁾ 0, MOSI⁽³⁾		0, WO1⁽³⁾	3, WO⁽³⁾			1, IN1
12	8	4	8	13	PC2	TWI Fm+	AIN30	0, AINN3 1, AINN3		3, ZCIN	1, XCK 0, RxD⁽³⁾	1, SCK 0, SCK⁽³⁾ 0, MISO⁽³⁾	0, SDA(C) 0, SDA(HC)⁽³⁾	0, WO2⁽³⁾			EVOUTC	1, IN2
13	9	5	9	14	PC3	TWI Fm+	AIN31	0, AINP4 1, AINP4			1, XDIR 0, XCK⁽³⁾	1, SS 0, SS⁽³⁾ 0, SCK⁽³⁾	0, SCL(C) 0, SCL(HC)⁽³⁾	0, WO3⁽³⁾				1, OUT
14	10	6	10	15	VDDIO2
15	-	-	-	-	GND
16	-	-	-	-	PC4						1, TxD⁽³⁾	1, MOSI⁽³⁾		0, WO4⁽³⁾
17	-	-	-	-	PC5						1, RxD⁽³⁾	1, MISO⁽³⁾		0, WO5⁽³⁾
18	-	-	-	-	PC6			0, OUT⁽³⁾ 1, OUT⁽³⁾ 2, OUT⁽³⁾			1, XCK⁽³⁾	1, SCK⁽³⁾	0, SDA(C)⁽³⁾		4, WO⁽³⁾			1, OUT⁽³⁾
19	-	-	-	-	PC7					0, ZCOUT⁽³⁾ 3, ZCOUT⁽³⁾	1, XDIR⁽³⁾	1, SS⁽³⁾	0, SCL(C)⁽³⁾				EVOUTC⁽³⁾
20	-	-	-	-	PD0		AIN0	0, AINN1 1, AINN1 2, AINN2						0, WO0⁽³⁾				2, IN0
21	11	7	11	-	PD1		AIN1			0, ZCIN				0, WO1⁽³⁾				2, IN1
22	12	8	12	-	PD2		AIN2	0, AINP0 1, AINP0 2, AINP0						0, WO2⁽³⁾			EVOUTD	2, IN2
23	13	9	13	-	PD3		AIN3	0, AINN0 1, AINP1						0, WO3⁽³⁾				2, OUT
24	14	10	14	16	PD4	VREFB	AIN4	1, AINP2 2, AINP1			0, TxD⁽³⁾	0, MOSI⁽³⁾		0, WO4⁽³⁾		WOC⁽³⁾			HEART⁽³⁾
25	15	11	15	17	PD5		AIN5	1, AINN0			0, RxD⁽³⁾	0, MISO⁽³⁾		0, WO5⁽³⁾		WOD⁽³⁾
26	16	12	16	18	PD6		AIN6	0, AINP3 1, AINP3 2, AINP3	OUT		0, XCK⁽³⁾ 1, TxD⁽³⁾	0, SCK⁽³⁾						2, OUT⁽³⁾
27	17	13	17	19	PD7	VREFA	AIN7	0, AINN2 1, AINN2 2, AINN0/AINN2			0, XDIR⁽³⁾ 1, RxD⁽³⁾	0, SS⁽³⁾					EVOUTD⁽³⁾
28	18	14	18	20	VDD
29	19	15	19	1	GND
30	-	-	-	-	PE0		AIN8	0, AINP1			4, TxD	0, MOSI⁽³⁾		0, WO0⁽³⁾
31	-	-	-	-	PE1		AIN9	2, AINP2			4, RxD	0, MISO⁽³⁾		0, WO1⁽³⁾
32	-	-	-	-	PE2		AIN10	0, AINP2			4, XCK	0, SCK⁽³⁾		0, WO2⁽³⁾			EVOUTE
33	-	-	-	-	PE3		AIN11				4, XDIR	0, SS⁽³⁾		0, WO3⁽³⁾
34	20	16	20	-	PF0	XTAL32K1	AIN16				2, TxD			0, WO0⁽³⁾		WOA⁽³⁾		3, IN0
35	21	17	21	-	PF1	XTAL32K2	AIN17				2, RxD			0, WO1⁽³⁾		WOB⁽³⁾		3, IN1
36	22	-	-	-	PF2	TWI Fm+	AIN18				2, XCK		1, SDA(HC)	0, WO2⁽³⁾		WOC⁽³⁾	EVOUTF	3, IN2
37	23	-	-	-	PF3	TWI Fm+	AIN19				2, XDIR		1, SCL(HC)	0, WO3⁽³⁾		WOD⁽³⁾		3, OUT
38	24	-	-	-	PF4		AIN20				2, TxD⁽³⁾			0, WO4⁽³⁾	0, WO⁽³⁾
39	25	-	-	-	PF5		AIN21				2, RxD⁽³⁾			0, WO5⁽³⁾	1, WO⁽³⁾				HEART⁽³⁾
40	26	18	22	2	RESET	RESET
41	27	19	23	3	UPDI	UPDI
42	28	20	24	-	VDD
43	29	21	25	-	GND

Note:

Pin names are of type Pxn, with x being the PORT instance (A, B, C, ...) and n the pin number. Notation for signals is PORTx_PINn. All pins can be used as event inputs.
All pins can be used for external interrupt, where pins Px2 and Px6 of each port have full asynchronous detection.
Alternative pin positions. To select alternative pin positions, refer to the Port Multiplexer section.
TWI pins are marked HC if they can be used as TWI Host or Client pins and C if they can only be used as TWI Client pins.

AVR® SD Product Brief

5.1 I/O Multiplexing