3.1 I/O Multiplexing


VQFN32, TQFP32	SPDIP28, SSOP28	VQFN28	VQFN20	SSOP20	SOIC14	Pin name ^(1,2)	Special	ADC0	AC0	USB	USARTn	SPI0	TWI0⁽⁴⁾	TCA0	TCBn	EVSYS	CCL
30	22	26	17	4	4	PA0	XTAL32K1⁽⁶⁾ XTALHF1 EXTCLK				0,TxD		SDA(HC)⁽³⁾	WO0			LUT0,IN0
31	23	27	18	5	5	PA1	XTAL32K2⁽⁶⁾ XTALHF2				0,RxD		SCL(HC)⁽³⁾	WO1			LUT0,IN1
32	24	28	19	6		PA2		AIN22			0,XCK 0,TxD⁽³⁾		SDA(HC)	WO2	0,WO	EVOUTA	LUT0,IN2
1	25	1	20	7		PA3		AIN23			0,XDIR 0,RxD⁽³⁾		SCL(HC)	WO3	1,WO		LUT0,OUT
2	26	2	1	8		PA4		AIN24			0,TxD⁽³⁾	MOSI		WO4
3	27	3	2	9		PA5		AIN25			0,RxD⁽³⁾	MISO		WO5
4	28	4	3	10		PA6		AIN26			0,XCK⁽³⁾	SCK					LUT0,OUT⁽³⁾
5	1	5	4	11		PA7	CLKOUT	AIN27	OUT		0,XDIR⁽³⁾	SS				EVOUTA⁽³⁾
6	2	6	5	12	6	VUSB				VUSB
7	3	7	6	13	7	DM				DM
8	4	8	7	14	8	DP				DP
9	5	9	8	15	9	PC3		AIN31	AINP4					WO3⁽³⁾			LUT1,OUT
10	6	10				PD0		AIN0	AINN1					WO0⁽³⁾			LUT2,IN0
11	7	11				PD1		AIN1						WO1⁽³⁾			LUT2,IN1
12	8	12				PD2		AIN2	AINP0					WO2⁽³⁾		EVOUTD	LUT2,IN2
13	9	13				PD3		AIN3	AINN0					WO3⁽³⁾			LUT2,OUT
14	10	14	9	16	10	PD4		AIN4			0,TxD⁽³⁾	MOSI⁽³⁾		WO4⁽³⁾
15	11	15	10	17	11	PD5		AIN5			0,RxD⁽³⁾	MISO⁽³⁾		WO5⁽³⁾
16	12	16	11	18	12	PD6		AIN6	AINP3		0,XCK⁽³⁾ 1,TxD⁽³⁾	SCK⁽³⁾					LUT2,OUT⁽³⁾
17	13	17	12	19	13	PD7	VREFA	AIN7	AINN2		0,XDIR⁽³⁾ 1,RxD⁽³⁾	SS⁽³⁾				EVOUTD⁽³⁾
18	14	18	13	20	14	VDD
19	15	19	14	1	1	GND
20	16	20				PF0	XTAL32K1	AIN16						WO0⁽³⁾			LUT3,IN0
21	17	21				PF1	XTAL32K2	AIN17						WO1⁽³⁾			LUT3,IN1
22						PF2		AIN18						WO2⁽³⁾		EVOUTF	LUT3,IN2
23						PF3		AIN19						WO3⁽³⁾			LUT3,OUT
24						PF4		AIN20						WO4⁽³⁾	0,WO⁽³⁾
25						PF5		AIN21						WO5⁽³⁾	1,WO⁽³⁾
26	18	22	15	2	2	PF6⁽⁵⁾	RESET
27	19	23	16	3	3	PF7	UPDI									EVOUTF⁽³⁾
28	20	24	13			VDD
29	21	25	14			GND

Note:

The pin names are Pxn type, with x being the PORT instance (A, B, C, ...) and n, the pin number. The notation for signals is PORTx_PINn. All pins can be used as event input.
All pins can be used for external interrupt.
Alternate pin positions. For selecting the alternate positions, refer to the PORTMUX - Port Multiplexer section.
The TWI pins that can be used as host or client are marked H. The pins with client-only are marked C.
Input-only.
Only for 14- and 20-pin devices.

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