The ATTINYXX provides you of 2, 4, 8 byres of In-System Programmable Flash, 128, 256, 512 bytes EEPROM, 128/256/256 bytes of SRAM, 6 IO lines, 32 working registers, 1 8bit timer/counter with compare modes, 1 8bit high speed timer/counter, USB, internal and external interrupts, 4 channel, 10-bit ADC, programmable watchdog timer with internal Oscillator, and 3 software selectable power saving modes.

The resulting architecture is more code efficient while achieving throughputs up to ten times faster than conventional CISC microcontrollers. The AVR core combines a rich instructions set with 32 general purpose working registers all 32 register are directly connected to the Arithmetic Logic Unit or ALU, allowing the two independent registers to be accessed in one single instruction executed in one clock cycle. See below block diagram or you can just download the datasheet located below. The ATTINY 25,45, and 85 is a low power CMOS 8 bit microcontroller base on AVR enhance RSICK architecture by executing powerful instruction in a single clock cycle the ATTINYXX achieves throughputs approaching 1 MIPS per MHz allowing you to optimize the power consumption v/s processing speed. In this illustration we will going to wire the ATTINY85 to control the OLED Screen using i2C Bus on ATTINY85 Microcontroller, I will just give an introduction what is ATTNY85 Microcontroller.

Attiny88 wire library