[avr-libc-dev] [bug #22240] Add EEPROM Page Size to header files

[Bob Paddock]

URL:
  <http://savannah.nongnu.org/bugs/?22240>

                 Summary: Add EEPROM Page Size to header files
                 Project: AVR C Runtime Library
            Submitted by: bpaddock
            Submitted on: Wednesday 02/06/2008 at 12:19
                Category: Header
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Header files
                  Status: None
        Percent Complete: 0%
             Assigned to: None
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any

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Details:

I would like to request the addition of the EEPROM Page Size
value to the header files, for the parts that have EEPROM.

The EEPROM Page Size value is located in the data sheet section
discussing Memory Programming.

Taking the AT90CAN64 as example, the EEPROM Page Size value is
eight, as found in Table 25-12.

The current iocan64.h file contains:

/* Constants */
#define    SPM_PAGESIZE 256
#define    RAMEND   0x10FF     /* Last On-Chip SRAM Location */
#define    XRAMEND  0xFFFF
#define    E2END    0x07FF
#define    FLASHEND 0xFFFF

I would like to see the following added:

#define E2PAGESIZE 8

Having this information in the header files will allow for
migration between parts of different sizes (All CANxx parts are
currently eight byte pages), as well as different AVR devices.

The reason for such a request is that if you need to save data in
the internal EEPROM, beyond the stated endurance for a byte,
listed in the data sheet as
"EEPROM (Endurance: 100,000 Write/Erase Cycles)", you need to
know how far to spread the bytes so that you can archive higher
endurance figures.  For example if you need a byte, but for
200,000 cycles you need to use two pages, or 16 bytes in the
CAN64 part.

The factory has confirmed, via my FAE, that the listed Endurance
figures are on a page bases, and not a byte bases.





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