[avrdude-dev] [bug #42267] jtag3isp fails to read lock and fuse bytes directly after changing lock byte

[Matthijs Kooijman]

URL:
  <http://savannah.nongnu.org/bugs/?42267>

                 Summary: jtag3isp fails to read lock and fuse bytes directly
after changing lock byte
                 Project: AVR Downloader/UploaDEr
            Submitted by: matthijs
            Submitted on: Fri 02 May 2014 09:43:30 AM GMT
                Category: None
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: None
                  Status: None
                 Privacy: Public
             Assigned to: None
         Originator Name: Matthijs Kooijman
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any

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Details:

I'm having some trouble reading and verifying the lock bits with jtag3isp.
jtag3 works as expected. I'm using Avrdude 6.0.1.

It seems that (shortly) after writing the lock byte, the fuse and lock bytes
no longer read correctly. When the clock is slower, only the first few reads
after the write fail, suggesting that this is somehow a timing problem.

The problem did not occur when writing the fuse bytes, only when writing the
lock byte.

See the attachment for an extensive log of commands and output, along with
inline comments by me showing the problem.

I haven't tried actually sniffing the SPI bus to see what values are actually
returned by the device being programmed. I might try that if you think it
helps (and my bus pirate is fast enough ;-p).



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File Attachments:


-------------------------------------------------------
Date: Fri 02 May 2014 09:43:30 AM GMT  Name: log.txt  Size: 44kB   By:
matthijs

<http://savannah.nongnu.org/bugs/download.php?file_id=31298>

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