STM32

STM32F4的原子操作怎么写？

2019-12-22 13:43发布

站内问答 / STM32/STM8
6099 3 3
void system_set_exec_alarm(uint8_t code) {
  uint8_t sreg = SREG;
  cli();
  sys_rt_exec_alarm = code;
  SREG = sreg;
}
上面的这个函数的意思是不是这样
把状态寄存器的数据保存到sreg这里。
然后关全局中断的函数cli();
变量赋值
还原状态寄存器的值
这个过程就是个 保存现场——执行原子操作——恢复现场 的过程，无论之前是否 I 置位，都不会发生错误或影响。
上面的函数是在AVR中实现的原子操作。
请问STM32F4中要实现这个操作怎么写
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2条回答
fengyunyu
1楼-- · 2019-12-22 14:20
http://bbs.21ic.com/icview-786350-1-1.html?source=1，LZ可以参考下
shangdawei
2楼-- · 2019-12-22 19:11
https://github.com/ARMmbed/mbed- ... orm/mbed_critical.h
https://github.com/ARMmbed/mbed- ... orm/mbed_critical.c


  1. bool core_util_atomic_cas_u8(uint8_t *ptr, uint8_t *expectedCurrentValue, uint8_t desiredValue)
  2. {
  3.     uint8_t currentValue = __LDREXB((volatile uint8_t*)ptr);
  4.     if (currentValue != *expectedCurrentValue) {
  5.         *expectedCurrentValue = currentValue;
  6.         __CLREX();
  7.         return false;
  8.     }

  10.     return !__STREXB(desiredValue, (volatile uint8_t*)ptr);
  11. }

  13. bool core_util_atomic_cas_u16(uint16_t *ptr, uint16_t *expectedCurrentValue, uint16_t desiredValue)
  14. {
  15.     uint16_t currentValue = __LDREXH((volatile uint16_t*)ptr);
  16.     if (currentValue != *expectedCurrentValue) {
  17.         *expectedCurrentValue = currentValue;
  18.         __CLREX();
  19.         return false;
  20.     }

  22.     return !__STREXH(desiredValue, (volatile uint16_t*)ptr);
  23. }


  26. bool core_util_atomic_cas_u32(uint32_t *ptr, uint32_t *expectedCurrentValue, uint32_t desiredValue)
  27. {
  28.     uint32_t currentValue = __LDREXW((volatile uint32_t*)ptr);
  29.     if (currentValue != *expectedCurrentValue) {
  30.         *expectedCurrentValue = currentValue;
  31.         __CLREX();
  32.         return false;
  33.     }

  35.     return !__STREXW(desiredValue, (volatile uint32_t*)ptr);
  36. }

  38. uint8_t core_util_atomic_incr_u8(uint8_t *valuePtr, uint8_t delta)
  39. {
  40.     uint8_t newValue;
  41.     do {
  42.         newValue = __LDREXB((volatile uint8_t*)valuePtr) + delta;
  43.     } while (__STREXB(newValue, (volatile uint8_t*)valuePtr));
  44.     return newValue;
  45. }

  47. uint16_t core_util_atomic_incr_u16(uint16_t *valuePtr, uint16_t delta)
  48. {
  49.     uint16_t newValue;
  50.     do {
  51.         newValue = __LDREXH((volatile uint16_t*)valuePtr) + delta;
  52.     } while (__STREXH(newValue, (volatile uint16_t*)valuePtr));
  53.     return newValue;
  54. }

  56. uint32_t core_util_atomic_incr_u32(uint32_t *valuePtr, uint32_t delta)
  57. {
  58.     uint32_t newValue;
  59.     do {
  60.         newValue = __LDREXW((volatile uint32_t*)valuePtr) + delta;
  61.     } while (__STREXW(newValue, (volatile uint32_t*)valuePtr));
  62.     return newValue;
  63. }


  66. uint8_t core_util_atomic_decr_u8(uint8_t *valuePtr, uint8_t delta)
  67. {
  68.     uint8_t newValue;
  69.     do {
  70.         newValue = __LDREXB((volatile uint8_t*)valuePtr) - delta;
  71.     } while (__STREXB(newValue, (volatile uint8_t*)valuePtr));
  72.     return newValue;
  73. }

  75. uint16_t core_util_atomic_decr_u16(uint16_t *valuePtr, uint16_t delta)
  76. {
  77.     uint16_t newValue;
  78.     do {
  79.         newValue = __LDREXH((volatile uint16_t*)valuePtr) - delta;
  80.     } while (__STREXH(newValue, (volatile uint16_t*)valuePtr));
  81.     return newValue;
  82. }

  84. uint32_t core_util_atomic_decr_u32(uint32_t *valuePtr, uint32_t delta)
  85. {
  86.     uint32_t newValue;
  87.     do {
  88.         newValue = __LDREXW((volatile uint32_t*)valuePtr) - delta;
  89.     } while (__STREXW(newValue, (volatile uint32_t*)valuePtr));
  90.     return newValue;
  91. }
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