Depending on the clock selection fuse settings, PB7 can be used as output from the inverting Oscillator
amplifier.
If the Internal Calibrated RC Oscillator is used as chip clock source, PB[7:6] is used as TOSC[2:1] input
for the Asynchronous Timer/Counter2 if the AS2 bit in ASSR is set.
5.2.4. Port C (PC[5:0])
Port C is a 7-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The PC[5:0]
output buffers have symmetrical drive characteristics with both high sink and source capability. As inputs,
Port C pins that are externally pulled low will source current if the pull-up resistors are activated. The Port
C pins are tri-stated when a reset condition becomes active, even if the clock is not running.
5.2.5. PC6/RESET
If the RSTDISBL Fuse is programmed, PC6 is used as an I/O pin. Note that the electrical characteristics
of PC6 differ from those of the other pins of Port C.
If the RSTDISBL Fuse is unprogrammed, PC6 is used as a Reset input. A low level on this pin for longer
than the minimum pulse length will generate a Reset, even if the clock is not running. Shorter pulses are
not guaranteed to generate a Reset.
The various special features of Port C are elaborated in the Alternate Functions of Port C section.
5.2.6. Port D (PD[7:0])
Port D is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The Port D
output buffers have symmetrical drive characteristics with both high sink and source capability. As inputs,
Port D pins that are externally pulled low will source current if the pull-up resistors are activated. The Port
D pins are tri-stated when a reset condition becomes active, even if the clock is not running.
5.2.7. AV
CC
AV
CC
is the supply voltage pin for the A/D Converter, PC[3:0], and PE[3:2]. It should be externally
connected to V
CC
, even if the ADC is not used. If the ADC is used, it should be connected to V
CC
through
a low-pass filter. Note that PC[6:4] use digital supply voltage, V
CC
.
5.2.8. AREF
AREF is the analog reference pin for the A/D Converter.
5.2.9. ADC[7:6] (TQFP and VFQFN Package Only)
In the TQFP and VFQFN package, ADC[7:6] serve as analog inputs to the A/D converter. These pins are
powered from the analog supply and serve as 10-bit ADC channels.
Atmel ATmega328/P [DATASHEET]
Atmel-42735B-328/P_Datasheet_Summary-11/2016
13
6. 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 6-1. PORT Function Multiplexing
(32-pin
MLF/TQFP)
Pin#
(28-pin
MLF) Pin#
(28-pin
PIPD) Pin#
PAD EXTINT PCINT ADC/AC OSC T/C #0 T/C
#1
USART 0 I2C 0 SPI 0
1 1 5 PD[3] INT1 PCINT19 OC2B
2 2 6 PD[4] PCINT20 T0 XCK0
4 3 7 VCC
3 4 8 GND
6 - - VCC
5 - - GND
7 5 9 PB[6] PCINT6 XTAL1/
TOSC1
8 6 10 PB[7] PCINT7 XTAL2/
TOSC2
9 7 11 PD[5] PCINT21 OC0B T1
10 8 12 PD[6] PCINT22 AIN0 OC0A
11 9 13 PD[7] PCINT23 AIN1
12 10 14 PB[0] PCINT0 CLKO ICP1
13 11 15 PB[1] PCINT1 OC1A
14 12 16 PB[2] PCINT2 OC1B SS0
15 13 17 PB[3] PCINT3 OC2A MOSI0
16 14 18 PB[4] PCINT4 MISO0
17 15 19 PB[5] PCINT5 SCK0
18 16 20 AVCC
19 - - ADC6 ADC6
20 17 21 AREF
21 18 22 GND
22 - - ADC7 ADC7
23 19 13 PC[0] PCINT8 ADC0
24 20 24 PC[1] PCINT9 ADC1
25 21 25 PC[2] PCINT10 ADC2
26 22 26 PC[3] PCINT11 ADC3
27 23 27 PC[4] PCINT12 ADC4 SDA0
28 24 28 PC[5] PCINT13 ADC5 SCL0
29 25 1 PC[6]/
RESET
PCINT14
Atmel ATmega328/P [DATASHEET]
Atmel-42735B-328/P_Datasheet_Summary-11/2016
14
(32-pin
MLF/TQFP)
Pin#
(28-pin
MLF) Pin#
(28-pin
PIPD) Pin#
PAD EXTINT PCINT ADC/AC OSC T/C #0 T/C
#1
USART 0 I2C 0 SPI 0
30 26 2 PD[0] PCINT16 RXD0
31 27 3 PD[1] PCINT17 TXD0
32 28 4 PD[2] INT0 PCINT18
Atmel ATmega328/P [DATASHEET]
Atmel-42735B-328/P_Datasheet_Summary-11/2016
15

ATMEGA328P-AU

Mfr. #:
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Microchip Technology / Atmel
Description:
8-bit Microcontrollers - MCU 32KB In-system Flash 20MHz 1.8V-5.5V
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