ATtiny84 — 14-Pin 8-Bit AVR Microcontroller with 8KB Flash (DIP-14)

Overview

The ATtiny84 (ATtiny84A) is a 14-pin 8-bit AVR RISC microcontroller manufactured by Microchip Technology (originally Atmel). Available in a compact DIP-14 through-hole and SOIC-14 surface-mount package, it bridges the gap between the compact 8-pin ATtiny85 (5 usable I/O lines) and the larger 28-pin ATmega328P.

Operating from $1.8\text{V}$ to $5.5\text{V}$ DC at up to $20\text{ MHz}$ , the ATtiny84 delivers $8\text{ KB}$ Flash, $512\text{ Bytes}$ SRAM, $512\text{ Bytes}$ EEPROM, an 8-channel 10-bit ADC with programmable $20\times$ differential gain, a 16-bit Timer1 with input capture, four hardware PWM outputs, and a Universal Serial Interface (USI for SPI and I2C). With full Arduino core support via Spence Konde's ATTinyCore, it is a popular choice for matrix keypad decoders, multi-sensor analog data nodes, and custom compact PCB modules requiring more pins than the ATtiny85 without the physical bulk of a 28-pin DIP chip.

Quick reference


CPU Core	8-bit AVR RISC Architecture
Package	14-pin DIP (DIP-14 / PDIP-14) / 14-pin SOIC / 20-pin QFN
Max Clock Frequency	$20\text{ MHz}$ ( $8\text{ MHz}$ calibrated internal RC)
Flash Memory	$8192\text{ Bytes}$ ( $8\text{ KB}$ ) non-volatile storage
SRAM	$512\text{ Bytes}$ internal RAM
EEPROM	$512\text{ Bytes}$ true non-volatile EEPROM
Supply Voltage Range	$1.8\text{ V}$ to $5.5\text{ V}$ DC ( $2.7\text{V} \dots 5.5\text{V}$ for $10\text{MHz}$ , $4.5\text{V} \dots 5.5\text{V}$ for $20\text{MHz}$ )
GPIO Count	12 Programmable I/O lines (Ports A and B)
Analog Peripherals	8-channel 10-bit ADC + $20\times$ Differential Gain + Internal Temp Sensor
Timers	1x 8-bit Timer0 + 1x 16-bit Timer1 with 4 PWM channels
Serial Bus	USI (Universal Serial Interface for SPI / I2C), ISP (SPI)

Pinout (DIP-14 Package)

text

                            ┌───┴───┐
                   VCC 1│ 1   14│ GND (0V)
     (PCINT8/XTAL1) PB0 2│       │13 PA0 (ADC0/AREF/PCINT0)
     (PCINT9/XTAL2) PB1 3│ATtiny │12 PA1 (ADC1/AIN0/PCINT1)
   (Active-Low/dW) PB3 4│  84   │11 PA2 (ADC2/AIN1/PCINT2)
    (PCINT10/INT0) PB2 5│DIP-14 │10 PA3 (ADC3/T0/PCINT3)
(ADC7/OC0B/ICP1) PA7 6│       │9  PA4 (ADC4/USCK/SCL/SCK)
(ADC6/OC0A/DI)   PA6 7│       │8  PA5 (ADC5/DO/MISO/OC1B)
                            └───────┘

Pin	Name	Type	Description
1	`VCC`	Power	Supply Voltage ( $+1.8\text{ V}$ to $+5.5\text{ V}$ DC)
2	`PB0`	GPIO / Clock	`XTAL1` (Crystal In) / `CLKI` / `PCINT8`
3	`PB1`	GPIO / Clock	`XTAL2` (Crystal Out) / `PCINT9`
4	`PB3`	GPIO / Reset	Active-LOW Reset / `dW` (debugWIRE) / `PCINT11`
5	`PB2`	GPIO / Digital	External Interrupt `INT0` / `OC0A` / `PCINT10`
6	`PA7`	GPIO / Analog	`ADC7` / `OC0B` (PWM) / Timer1 `ICP1` / `PCINT7`
7	`PA6`	GPIO / SPI	`MOSI` (ISP) / `ADC6` / `OC0A` / USI Data Input `DI` / `SDA`
8	`PA5`	GPIO / SPI	`MISO` (ISP) / `ADC5` / `OC1B` (PWM) / USI Data Output `DO`
9	`PA4`	GPIO / SPI	`SCK` (ISP) / `ADC4` / USI Clock `USCK` / `SCL`
10, 11, 12	`PA3`-`PA1`	GPIO / Analog	`ADC3`-`ADC1` / Analog Comparator `AIN0`/`AIN1`
13	`PA0`	GPIO / Analog	`ADC0` / Analog Reference `AREF`
14	`GND`	Power	Common Ground reference ( $0\text{ V}$ )

Minimal Circuit & ISP Flashing Hookup

text

   Arduino as ISP / USBasp Programmer
   ┌────────────────────────────────┐
   │ 5V / 3.3V ─────────────────────┼─────────┬──────────────► [Pin 1: VCC]
   │                                │         │                     ATtiny84
   │                                │   [ 100nF Cap ]               DIP-14
   │                                │         │
   │ GND ───────────────────────────┼─────────┼──────────────► [Pin 14: GND]
   │ RESET (Pin 10 on Arduino) ─────┼─────────┼──────────────► [Pin 4: PB3 / RESET]
   │ MOSI (Pin 11 on Arduino) ──────┼─────────┼──────────────► [Pin 7: PA6 / MOSI]
   │ MISO (Pin 12 on Arduino) ──────┼─────────┼──────────────► [Pin 8: PA5 / MISO]
   │ SCK  (Pin 13 on Arduino) ──────┼─────────┼──────────────► [Pin 9: PA4 / SCK]
   └────────────────────────────────┘

Comparison: ATtiny84 vs ATtiny85 vs ATmega328P

Parameter	ATtiny85	ATtiny84	ATmega328P
Package	8-pin DIP	14-pin DIP	28-pin DIP
Usable GPIOs	5 GPIOs	12 GPIOs	23 GPIOs
Flash Memory	$8\text{ KB}$	$8\text{ KB}$	$32\text{ KB}$
ADC Channels	4 channels	8 channels	6 channels (DIP)
16-bit Timers	0 (two 8-bit)	1x 16-bit Timer1	1x 16-bit Timer1

Common mistakes

SPI pin mapping confusion: On the ATtiny85, SPI pins are on PB0/PB1/PB2. On the ATtiny84, SPI pins (MOSI, MISO, SCK) are located on PA6, PA5, PA4. Double-check wiring when porting designs from ATtiny85 to ATtiny84.
Floating RESET pin: In electrically noisy motor or relay driver environments, pull Pin 4 (RESET) up to VCC using an external $10\text{ k}\Omega$ resistor.

Notes

Arduino Core: Fully supported by Spence Konde's open-source ATTinyCore board package.