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avr_atmega_328_fuses

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AVR ATmega 328/328p Fuses

If you encounter errors see Errors from AVRdude
For all fuses

Fuse stateDescription
1Unprogrammed
0Programmed

Find your programmer

nonexistent is just a variable to make the command generate output

avrdude -c nonexistent

This produces a list of all the programmers supported by avrdude so you can see if you have one and if so what its name is for avrdude
See avrdude for reading flash and eeprom

Arduino UNO Default fuse settings

First the default Atmel AVR factory fusesettings

LFF0110 0010
HD91101 1001
EFF1111 1111

From the boards.txt file found in the Arduino IDE version 1.8.9

LFF1111 1111uno.bootloader.low_fuses
HDE1101 1110uno.bootloader.high_fuses
EFD1111 1101uno.bootloader.extended_fuses

So far we found three different default fuse settings
Fresh ATmega328P-PU from China. (On a ZIF USB-B prototyping board with 2 3mm LED's and probably the Arduino Optiboot bootloader)

LFF1111 1111
HDE1101 1110
EFD1111 1101

From Arduino default fuse settings on coding with Cody

LFF1111 1111
HDE1101 1110
E050000 0101

From Arduino atmega 328p fuse settings on Martyn Currey

L620110 0010
HD91101 1001
EFF1111 1111

Read fuses

These three commands will read all three fuse blocks. Only the fuse block specified will be written to the specified file
Send the fuseseeting to a file ( - is stdout )

low fuses

avrdude -c usbasp -p m328p -P USB -b 57600 -U lfuse:r:/tmp/extendedfuses.txt:i -v

high fuses

avrdude -c usbasp -p m328p -P USB -b 57600 -U hfuse:r:/tmp/highfuses.txt:i -v

extended fuses

avrdude -c usbasp -p m328p -P USB -b 57600 -U efuse:r:/tmp/extendedfuses.txt:i

Reset the fuses

See:

AVR High voltage programming Fuses rescueFuse settings output after flashing the hex code with avrdude -c usbasp -p m8 -P USB -b 57600 -U flash:w:Rescue.hex: avrdude: safemode: Fuses OK (E:FF, H:D9, L:E1)
AVR rescue
ArduinoISP reading writing fuses on the ATmega328P

Set the fuses

Warning

Setting some specific fuses will cause ISP to be disabled because SPI programming will be disabled. So take care when you want to

  • Disable the reset pin
  • Enable debugWIRE

You will need one of

  • High Voltage (HV) programmer
  • Parallel programmer
  • A programmer with debugWIRE

to reset and change back those fuses

Low byte fuses

These set the clock

NameBitDescriptionDefault ValueRemark
CKDIV87Divide clock by 80Change to 1 for Arduino
CKOUT6Clock output1Clock is also on the CLKO pin. This is the system clock
SUT15Select start-up time1
SUT04Select start-up time0Change to 1 for Arduino
CKSEL33Select clock source0Change to 1 for Arduino
CKSEL22Select clock source0Change to 1 for Arduino
CKSEL11Select clock source1
CKSEL00Select clock source0Change to 1 for Arduino

The default value of the low fusebyte is 0110 0010 being 0x62 in hex
For Arduino we need 1111 1111 being 0xFF in hex
For Arduino without bootloader we need 1111 1111 being 0xFF in hex

CKSEL3..1 = 111 means:

Frequency Range (MHz)8.0 - 16.0
Recommended Range for Capacitors C1 and C2 (pF)12 - 22

CKSEL0 = 1 and SUT1..0 = 11 means:

Crystal Oscillator, slowly rising power
Start-up Time from Power-down and Power-save16000 clockcycles
Additional Delay from Reset (VCC = 5.0V)14 cClockcycles + 65ms

CKSEL Device Clocking Options

Bits 3..0

BitsDescriptionRemark
1111 - 1000Low power crystal oscillatorWorks with a quartz crystal or a ceramic resonator
0111 - 0110Full swing crystal oscillatorIs this a bug in the datasheet? CKSEL0=0 is mainly ceramic resonator
0111Full swing crystal oscillator0,4-20MHz
0101Low frequency crystal oscillatorStart-up time from Power-down and Power-save: 32K CK → Stable frequency at start-up
0100Low frequency crystal oscillatorStart-up time from Power-down and Power-save 1K CK
0011Internal 128kHz RC oscillator
0010Calibrated internal RC oscillatorRuns at nominal 8MHz (7,3 - 8,1 MHz). This is the default fuse setting
0001Reserved
0000External clock

High byte fuses

BitNameDescriptionDefault ValueRemark
7RSTDISBLExternal Reset Disable1
6DWENdebugWIRE Enable1
5SPIENEnable Serial Program and Data Downloading0SPI programming enabled
4WDTONWatchdog Timer Always On1
3EESAVEEEPROM memory is preserved through the Chip Erase1EEPROM not reserved
2BOOTSZ1Select Boot Size0Change to 1 for Arduino when Optiboot is used
1BOOTSZ0Select Boot Size0Change to 1 for Arduino when Optiboot is used
0BOOTRSTSelect Reset Vector1Change to 0 for Arduino

The default value of the high fusebyte is 1101 1001 being 0xD9 in hex
For Arduino we need 1101 1110 being 0xDE in hex
For Arduino without bootloader we need 1101 1111 being 0xD? in hex. Also the IVSEL flag needs to be set in the MCUCR register
If no Boot Loader capability is needed, the entire Flash is available for application code
The Interrupt Vectors can be moved to the start of the Boot Flash section by setting the IVSEL bit in the MCU Control Register (MCUCR)
The Reset Vector can also be moved to the start of the Boot Flash section by programming the BOOTRST Fuse
BOOTSZ1..0 = 11 means:

Boot Size128 words
Pages4
Application Flash Section0x000 - 0xF7F
Boot Loader Flash Section0xF80 - 0xFFF
End Application Section0xF7F
Boot Reset Address0xF80(Start Boot Loader Section)

Extended byte fuses

BitNameDescriptionDefaultRemark
7
6
5
4
3
2BODLEVEL2Brown-out Detector trigger level1
1BODLEVEL1Brown-out Detector trigger level1Change to 0 for Arduino
0BODLEVEL0Brown-out Detector trigger level1

The default value of the low fusebyte is 1111 1111 being 0xFF in hex
For Arduino we need 1111 1101 being 0xFD in hex
For Arduino without bootloader we need 1111 1101 being 0xFD in hex

BODLEVEL Fuse Coding

BitsMin. VBOT (V)Typ VBOT (V)Max VBOT (V)
111BOD DisabledBOD DisabledBOD Disabled
1101,71,82,0
1012,52,72,9
1004.14,34,5

Boot Lock bits

For us all boot lock bits need to be set to 1 (high) so there is boot locking and all of flash can be programmed. This is the default value.

Reference

Arduino ATmega 328p fuse settings
How to change fuse bits of AVR Atmega328p
ATmega 328 reading info
Search for atmega-fusebit-doctor-hvpp


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avr_atmega_328_fuses.txt · Last modified: 16-01-2020 00:31 by wim