[avr-libc-dev] [bug #19669] Need function to read signature row

[Bill Johnson]

URL:
  <http://savannah.nongnu.org/bugs/?19669>

                 Summary: Need function to read signature row 
                 Project: AVR C Runtime Library
            Submitted by: billj
            Submitted on: Monday 04/23/2007 at 20:39
                Category: Header
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Header files
                  Status: None
                 Privacy: Public
        Percent Complete: 0%
             Assigned to: None
        Originator Email: address@hidden
             Open/Closed: Open
         Discussion Lock: Any

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Details:

Greetings,
The ATmega406 (and some others?) allows access to a signature row of data. It
contains signature bytes as well as device specific factory calibration
values. I can find no libc function to access it. It requires special timing
to access the data space. There is a discussion about it at:
http://www.avrfreaks.net/index.php?name=PNphpBB2&file=viewtopic&t=48859

I have a possible fix below. It seems to work OK but I don't know inline ASM
macro language and pieced it together from similar macros so it could have
some issues. From discussion it should probably go in boot.h. Interrupts
should be disabled during use, maybe that should be in the macro.
+BillJ

/** \ingroup avr_boot
    \def signature_byte_get(address)

    Read the Signature Row byte at \c address.

    Parameter \c address can be 0-0x1f as define for supporting processors.
    \note The values are processor dependent.
*/

#define __BOOT_SIGROW_READ         (_BV(SPMEN) | _BV(SIGRD))
          
#define signature_byte_get(addr)             \
(__extension__({                             \
    uint16_t __addr16 = (uint16_t)(addr);    \
    uint8_t __result;                        \
    __asm__                                  \
    (                                        \
        "sts %1, %2\n\t"                     \
        "lpm %0, Z" "\n\t"                   \
        : "=r" (__result)                    \
        : "i" (_SFR_MEM_ADDR(__SPM_REG)),    \
          "r" ((uint8_t) __BOOT_SIGROW_READ),\
          "z" (__addr16)                     \
    );                                       \
    __result;                                \
}))





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