[avr-libc-dev] [bug #37772] wdt_enable() doesn't work for a list of chips

[anonymous]

URL:
  <http://savannah.nongnu.org/bugs/?37772>

                 Summary: wdt_enable() doesn't work for a list of chips
                 Project: AVR C Runtime Library
            Submitted by: None
            Submitted on: Пнд 19 Ноя 2012 07:29:10
                Category: Header
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Header files
                  Status: None
        Percent Complete: 0%
             Assigned to: None
        Originator Email: address@hidden
             Open/Closed: Open
         Discussion Lock: Any
                 Release: Any
           Fixed Release: None

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Details:

wdt can't be enabled because of wrong assembler instruction order in wdt.h


#define wdt_enable(value)   \
__asm__ __volatile__ (  \
    "in __tmp_reg__,__SREG__" "\n\t"    \
    "cli" "\n\t"    \
    "wdr" "\n\t"    \
    "sts %0,%1" "\n\t"  \
    "out __SREG__,__tmp_reg__" "\n\t"   \
    "sts %0,%2" "\n\t" \
    : /* no outputs */  \
    : "M" (_SFR_MEM_ADDR(_WD_CONTROL_REG)), \
    "r" (_BV(_WD_CHANGE_BIT) | _BV(WDE)), \
    "r" ((uint8_t) ((value & 0x08 ? _WD_PS3_MASK : 0x00) | \
        _BV(WDE) | (value & 0x07)) ) \
    : "r0"  \
)


"sts" instructions must follow one another, as they must be completed within 4
clock cycles (according to datasheets)

So, correct version is this:

#define wdt_enable(value)   \
__asm__ __volatile__ (  \
    "in __tmp_reg__,__SREG__" "\n\t"    \
    "cli" "\n\t"    \
    "wdr" "\n\t"    \
    "sts %0,%1" "\n\t"  \
    "sts %0,%2" "\n\t"  \
    "out __SREG__,__tmp_reg__" "\n\t"   \
    : /* no outputs */  \
    : "M" (_SFR_MEM_ADDR(_WD_CONTROL_REG)), \
    "r" (_BV(_WD_CHANGE_BIT) | _BV(WDE)), \
    "r" ((uint8_t) ((value & 0x08 ? _WD_PS3_MASK : 0x00) | \
        _BV(WDE) | (value & 0x07)) ) \
    : "r0"  \
)





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