[avr-libc-dev] [bug #21410] Incorrect use of 16-bit eeprom addresses in devices with 8-Bit address registers

[Robert von Knobloch]

URL:
  <http://savannah.nongnu.org/bugs/?21410>

                 Summary: Incorrect use of 16-bit eeprom addresses in devices
with 8-Bit address registers
                 Project: AVR C Runtime Library
            Submitted by: robertvknobloch
            Submitted on: Wednesday 24/10/07 at 07:53
                Category: None
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: libc code
                  Status: None
        Percent Complete: 0%
             Assigned to: None
        Originator Email: address@hidden
             Open/Closed: Open
         Discussion Lock: Any

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Details:

The library functions, defined in avr-libc-1.4.6/libc/misc/eeprom.S"
always write a 16-Bit address to the EEAR register. This is expressly
forbidden in the Tiny13 datasheet and appears to cause faulty reading of the
eeprom data under some circumstances.

Reference:
Tiny 13 datasheet on page 158, note 1: "Reserved I/O memory
addresses should never be written".
The same appears for the 8515 and 2313 (these are expressly mentioned in
'eeprom.S').

My proposal is to modify eeprom.S to write 16 bit addresses where the
ioxxyy.h file defines EEARH and 8 bit to all others (seems OK for newer
devices, I don't have experience of the older parts).




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