0xFD Fuse Low Byte on 16 MHz ATmega328 boards?

Other Hardware 3rd Party Boards
1

I have quite a few Arduino Pro Mini and Arduino Nano boards with 16 MHz crystals that arrived with the ATmega328's Fuse Low Byte programmed as 0xfd which is strange because that would be:

Ext. Crystal Osc.; Frequency 3.0-8.0 MHz; Start-up time PWRDWN/RESET: 16K CK/14 CK + 65 ms; [CKSEL=1101 SUT=11]

Has anyone else encountered such Fuse Low Byte on 16 MHz AVR boards?

They do work well but still, I might change the low fuse byte to 0xff which is:

Ext. Crystal Osc.; Frequency 8.0- MHz; Start-up time PWRDWN/RESET: 16K CK/14 CK + 65 ms; [CKSEL=1111 SUT=11]

Here is the output from the ATMEL_Autodetect.ipr script for the iProg programmer and I am getting the same results using DIY parallel port programmer with PonyProg2000:

Detect AVR...OK
Signature: 1E950F
MCU detected: ATMEGA328P
Detect AVR...OK
Read FUSES...
Fuse extend byte = 0xFD (11111101)
Fuse high byte = 0xDA (11011010)
Fuse low byte = 0xFF (11111111)
Detect AVR...OK
Read Lock Bit Byte...
Lock Bit Byte = 0xFF (11111111)

And some of them have locked bootloader:

Detect AVR...OK
Signature: 1E950F
MCU detected: ATMEGA328P
Detect AVR...OK
Read FUSES...
Fuse extend byte = 0xFD (11111101)
Fuse high byte = 0xDA (11011010)
Fuse low byte = 0xFF (11111111)
Detect AVR...OK
Read Lock Bit Byte...
Lock Bit Byte = 0xCF (11001111)
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Low/high/extended = FF/DA/FD is how all the 16MHz 328P boards are listed in boards.txt.

1 Like
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My mistake - I swapped the fuses by mistake because online fuse calculator lists them in the order LOW - HIGH - EXTENDED and the programer's script lists them in the order EXTENDED - HIGH - LOW.

I entered the extended byte read by the programmer at the place of low byte in the online calculator's form and saw the frequency doesn't match and since I swapped the low and extendend bytes I thought 0xfd should be changed into 0xff while in fact everything is OK :-/

I was always using PonyProg where there is UI for setting the fuses so I didn't recognise them as hex values.

Thank you very much!

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