[avrdude-dev] [bug #51664] compare of unused efuse bits fail

[Martin Pischky]

URL:
  <http://savannah.nongnu.org/bugs/?51664>

                 Summary: compare of unused efuse bits fail
                 Project: AVR Downloader/UploaDEr
            Submitted by: pischky
            Submitted on: Sat 05 Aug 2017 09:53:11 AM UTC
                Category: None
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: None
                  Status: None
                 Privacy: Public
             Assigned to: None
         Originator Name: Martin Pischky
        Originator Email: 
             Open/Closed: Open
                 Release: 6.3
         Discussion Lock: Any
     Programmer hardware: avrispv2 or avrdude_isp
             Device type: Atmega328P

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Details:

With -U efuse:w:0x05:m we get the meassge:
~~~~~
Writing | ################################################## | 100% 0.02s

avrdude.exe: 1 bytes of efuse written
avrdude.exe: verifying efuse memory against 0x05:
avrdude.exe: load data efuse data from input file 0x05:
avrdude.exe: input file 0x05 contains 1 bytes
avrdude.exe: reading on-chip efuse data:

Reading | ################################################## | 100% -0.00s

avrdude.exe: verifying ...
avrdude.exe: verification error, first mismatch at byte 0x0000
             0xfd != 0x05
avrdude.exe: verification error; content mismatch
~~~~~

The difference are the undefined bits in the efuses (3 to 7). 

As far as I understand from datasheet and use with atmel tools these should be
spezified as "1" but for older versions of avrdude (5.1? to 6.1) these had to
be set to "0" to avoid abort on programming. Now on switching from AVRDude 6.1
to 6.3 this is not working anymore and the programming gets aborted and the
fuses remain unchanged.

I guess this may be related to bug #22248 (and #21954).

>From SVN I can see that with revision r1335 the part definition has been
changed (part/id="m328"/memory "efuse"/read) for the bits 3 to 7 from "x" to
"o". I did not know what the effect of this change is.

I would suggest that these bits are ignored in the compare to be compatible
with older versions of AvrDude.




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