ATmega328

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ATmega328P in a 28-pin dual inline package (DIP)
Die of ATmega328P

The ATmega328 is a single-chip microcontroller created by Atmel in the megaAVR family.

Specifications[edit]

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 (8-channels in TQFP and QFN/MLF packages), 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.[1]

Key parameters[edit]

Parameter Value
CPU type 8-bit AVR
Performance 20 MIPS at 20 MHz[2]
Flash memory 32 kB
SRAM 2 kB
EEPROM 1 kB
Pin count 28-pin PDIP, MLF, 32-pin TQFP, MLF[2]
Maximum operating frequency 20 MHz
Number of touch channels 16
Hardware QTouch Acquisition No
Maximum I/O pins 26
External interrupts 2
USB Interface No
USB Speed

Series alternatives[edit]

A common alternative to the ATmega328 is the "picoPower" ATmega328P. A comprehensive list of all other member of the megaAVR series can be found on the Atmel website.[3]

Applications[edit]

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[citation 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[edit]

Pinout of ATmega 48A/PA/88A/PA/168A/PA/328/P in 28-PDIP (datasheet)

Reliability qualification shows that the projected data retention failure rate is much less than 1 PPM over 20 years at 85 °C or 100 years at 25 °C.[4]

Parallel program mode[2]
Programming signal Pin Name I/O Function
RDY/BSY PD1 O High means the MCU is ready for a new command, otherwise busy.
OE PD2 I Output Enable (Active low)
WR PD3 I Write Pulse (Active low)
BS1 PD4 I Byte Select 1 (“0” = Low byte, “1” = High byte)
XA0 PD5 I XTAL Action bit 0
XA1 PD6 I XTAL Action bit 1
PAGEL PD7 I Program memory and EEPROM Data Page Load
BS2 PC2 I Byte Select 2 (“0” = Low byte, “1” = 2nd High byte)
DATA PC[1:0]:PB[5:0] I/O Bi-directional data bus (Output when OE is low)

Programming mode is entered when PAGEL (PD7), XA1 (PD6), XA0 (PD5), BS1 (PD4) is set to zero.[2] 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.[2] 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 (PD1) goes high. XA1:XA0:BS1:DATA = 100 0001 0000, XTAL1 pulse, pulse WR to zero. This is the Flash write command.[2] And so on..

Serial Programming[2]
Symbol Pins I/O Description
MOSI PB3 I Serial data in
MISO PB4 O Serial Data out
SCK PB5 I Serial 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 (0x53) will be echoed back by the MCU.[2]

See also[edit]

Notes[edit]

  1. ^ "ATmega328P". Retrieved 2016-07-14. 
  2. ^ a b c d e f g h "Atmel 8-bit AVR Microcontrollers ATmega328/P Datasheet Complete" (PDF). Retrieved 2016-07-14. 
  3. ^ "megaAVR Microcontrollers". Atmel. Retrieved 2016-07-14. 
  4. ^ "Atmel 8-bit AVR Microcontrollers ATmega328/P Datasheet Summary" (PDF). June 2016. Retrieved 2016-07-14. 

External links[edit]