ATmega328


The ATmega328 is a single-chip microcontroller created by Atmel in the megaAVR family. It has a modified Harvard architecture 8-bit RISC processor core.

Specifications

The Atmel 8-bit AVR RISC-based microcontroller combines 32 KB ISP flash memory with read-while-write capabilities, 1 KB EEPROM, 2 KB SRAM, 23 general purpose I/O lines, 32 general purpose working registers, three flexible timer/counters with compare modes, internal and external interrupts, serial programmable USART, a byte-oriented 2-wire serial interface, SPI serial port, 6-channel 10-bit A/D converter, programmable watchdog timer with internal oscillator, and five software selectable power saving modes. The device operates between 1.8-5.5 volts.
The device achieves throughput approaching 1 MIPS per MHz.

Features

Family

A common alternative to the ATmega328 is the "picoPower" ATmega328P. A comprehensive list of all other members of the megaAVR series can be found on the Atmel website.
As of 2013 the ATmega328 is commonly used in many projects and autonomous systems where a simple, low-powered, low-cost micro-controller is needed. Perhaps the most common implementation of this chip is on the popular Arduino development platform, namely the Arduino Uno and Arduino Nano models.

Programming

Reliability qualification shows that the projected data retention failure rate is much less than over 20 years at 85 °C or 100 years at 25 °C.
Programming signalPin NameI/OFunction
RDY/BSYPD1OHigh means the MCU is ready for a new command, otherwise busy.
OEPD2IOutput Enable
WRPD3IWrite Pulse
BS1PD4IByte Select 1
XA0PD5IXTAL Action bit 0
XA1PD6IXTAL Action bit 1
PAGELPD7IProgram memory and EEPROM Data Page Load
BS2PC2IByte Select 2
DATAPC:PBI/OBi-directional data bus

Programming mode is entered when PAGEL, XA1, XA0, BS1 is set to zero. RESET pin to 0V and VCC to 0V. VCC is set to 4.5 - 5.5V. Wait 60 μs, and RESET is set to 11.5 - 12.5 V. Wait more than 310 μs. Set XA1:XA0:BS1:DATA = 100 1000 0000, pulse XTAL1 for at least 150 ns, pulse WR to zero. This starts the Chip Erase. Wait until RDY/BSY goes high. XA1:XA0:BS1:DATA = 100 0001 0000, XTAL1 pulse, pulse WR to zero. This is the Flash write command. And so on..
SymbolPinsI/ODescription
MOSIPB3ISerial data in
MISOPB4OSerial Data out
SCKPB5ISerial Clock

Serial data to the MCU is clocked on the rising edge and data from the MCU is clocked on the falling edge. Power is applied to VCC while RESET and SCK are set to zero. Wait for at least 20 ms and then the Programming Enable serial instruction 0xAC, 0x53, 0x00, 0x00 is sent to the MOSI pin. The second byte will be echoed back by the MCU.