3.1 I/O Multiplexing


VQFN48/ TQFP48	VQFN32/ TQFP32	SOIC28/SSOP28/ SPDIP28	Pin name^(1,2)	Special	ADC0	ACn	DAC0	OPAMP	ZCDn	USARTn	SPIn	TWIn⁽⁴⁾	TCAn	TCBn	TCD0	EVSYS	CCL-LUTn
44	30	22	PA0	XTALHF1 EXTCLK						0, TxD			0, WO0				0, IN0
45	31	23	PA1	XTALHF2						0, RxD			0, WO1				0, IN1
46	32	24	PA2	TWI Fm+						0, XCK		0, SDA(HC)	0, WO2	0, WO		EVOUTA	0, IN2
47	1	25	PA3	TWI Fm+						0, XDIR		0, SCL(HC)	0, WO3	1, WO			0, OUT
48	2	26	PA4							0, TxD⁽³⁾	0, MOSI		0, WO4		WOA
1	3	27	PA5							0, RxD⁽³⁾	0, MISO		0, WO5		WOB
2	4	28	PA6							0, XCK⁽³⁾	0, SCK				WOC		0, OUT⁽³⁾
3	5	1	PA7	CLKOUT		0, OUT 1, OUT 2, OUT			0, OUT 1, OUT	0, XDIR⁽³⁾	0, SS				WOD	EVOUTA⁽³⁾
4			PB0							3, TxD			0, WO0⁽³⁾ 1, WO0				4, IN0
5			PB1							3, RxD			0, WO1⁽³⁾ 1, WO1				4, IN1
6			PB2	TWI						3, XCK		1, SDA(HC)⁽³⁾	0, WO2⁽³⁾ 1, WO2			EVOUTB	4, IN2
7			PB3	TWI						3, XDIR		1, SCL(HC)⁽³⁾	0, WO3⁽³⁾ 1, WO3				4, OUT
8			PB4							3, TxD⁽³⁾	1, MOSI⁽³⁾		0, WO4⁽³⁾ 1, WO4	2, WO⁽³⁾	WOA⁽³⁾
9			PB5							3, RxD⁽³⁾	1, MISO⁽³⁾		0, WO5⁽³⁾ 1, WO5	3, WO	WOB⁽³⁾
10	6	2	PC0							1, TxD	1, MOSI		0, WO0⁽³⁾	2, WO			1, IN0
11	7	3	PC1							1, RxD	1, MISO		0, WO1⁽³⁾	3, WO⁽³⁾			1, IN1
12	8	4	PC2	TWI Fm+						1, XCK	1, SCK	0, SDA(HC)⁽³⁾	0, WO2⁽³⁾			EVOUTC	1, IN2
13	9	5	PC3	TWI Fm+						1, XDIR	1, SS	0, SCL(HC)⁽³⁾	0, WO3⁽³⁾				1, OUT
14	10	6	VDDIO2
15			GND
16			PC4							1, TxD⁽³⁾	1, MOSI⁽³⁾		0, WO4⁽³⁾ 1, WO0⁽³⁾
17			PC5							1, RxD⁽³⁾	1, MISO⁽³⁾		0, WO5⁽³⁾ 1, WO1⁽³⁾
18			PC6			0, OUT⁽³⁾ 1, OUT⁽³⁾ 2, OUT⁽³⁾				1, XCK⁽³⁾	1, SCK⁽³⁾	0, SDA(C)⁽³⁾	1, WO2⁽³⁾				1, OUT⁽³⁾
19			PC7						0, OUT⁽³⁾ 1, OUT⁽³⁾	1, XDIR⁽³⁾	1, SS⁽³⁾	0, SCL(C)⁽³⁾				EVOUTC⁽³⁾
20			PD0		AIN0	0, AINN1 1, AINN1 2, AINN1							0, WO0⁽³⁾				2, IN0
21	11	7	PD1		AIN1			OP0, INP	0, ZCIN				0, WO1⁽³⁾				2, IN1
22	12	8	PD2		AIN2	0, AINP0 1, AINP0 2, AINP0		OP0, OUT					0, WO2⁽³⁾			EVOUTD	2, IN2
23	13	9	PD3		AIN3	0, AINN0 1, AINP1		OP0, INN					0, WO3⁽³⁾				2, OUT
24	14	10	PD4		AIN4	1, AINP2 2, AINP1		OP1, INP					0, WO4⁽³⁾
25	15	11	PD5		AIN5	1, AINN0		OP1, OUT					0, WO5⁽³⁾
26	16	12	PD6		AIN6	0, AINP3 1, AINP3 2, AINP3	OUT										2, OUT⁽³⁾
27	17	13	PD7	VREFA	AIN7	0, AINN2 1, AINN2 2, AINN0/AINN2		OP1, INN								EVOUTD⁽³⁾
28	18	14	AVDD
29	19	15	AGND
30			PE0		AIN8	0, AINP1				4, TxD	0, MOSI⁽³⁾		0, WO0⁽³⁾
31			PE1		AIN9	2, AINP2		OP2, INP		4, RxD	0, MISO⁽³⁾		0, WO1⁽³⁾
32			PE2		AIN10	0, AINP2		OP2, OUT		4, XCK	0, SCK⁽³⁾		0, WO2⁽³⁾			EVOUTE
33			PE3		AIN11			OP2, INN	1, ZCIN	4, XDIR	0, SS⁽³⁾		0, WO3⁽³⁾
34	20	16	PF0	XTAL32K1	AIN16⁽⁵⁾					2, TxD			0, WO0⁽³⁾		WOA⁽³⁾		3, IN0
35	21	17	PF1	XTAL32K2	AIN17⁽⁵⁾					2, RxD			0, WO1⁽³⁾		WOB⁽³⁾		3, IN1
36	22		PF2	TWI Fm+	AIN18⁽⁵⁾					2, XCK		1, SDA(HC)	0, WO2⁽³⁾		WOC⁽³⁾	EVOUTF	3, IN2
37	23		PF3	TWI Fm+	AIN19⁽⁵⁾					2, XDIR		1, SCL(HC)	0, WO3⁽³⁾		WOD⁽³⁾		3, OUT
38	24		PF4		AIN20⁽⁵⁾					2, TxD⁽³⁾			0, WO4⁽³⁾	0, WO⁽³⁾
39	25		PF5		AIN21⁽⁵⁾					2, RxD⁽³⁾			0, WO5⁽³⁾	1, WO⁽³⁾
40	26	18	PF6⁽⁶⁾	RESET
41	27	19	UPDI	UPDI
42	28	20	VDD
43	29	21	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.
AIN16 - AIN21 cannot be used as a negative ADC input for differential measurements.
Input only.