STM32 串口固件库中定义的几个中断标志什么意思？

STM32 串口固件库中定义的几个中断标志位什么意思?

#define USART_IT_PE ((uint16_t)0x0028)
#define USART_IT_TXE ((uint16_t)0x0727)
#define USART_IT_TC ((uint16_t)0x0626)
#define USART_IT_RXNE ((uint16_t)0x0525)
#define USART_IT_IDLE ((uint16_t)0x0424)
#define USART_IT_LBD ((uint16_t)0x0846)
#define USART_IT_CTS ((uint16_t)0x096A)
#define USART_IT_ERR ((uint16_t)0x0060)
#define USART_IT_ORE ((uint16_t)0x0360)
#define USART_IT_NE ((uint16_t)0x0260)
#define USART_IT_FE ((uint16_t)0x0160)

可见，在stm32f10x_usart.h中宏定义的以上几个宏，很没有规律，咋一看还真不知道为什么会这么定义，其实通过代码就很容易明白：
D7~D5：代表中断标志位对应的中断使能位在 CR1、CR2还是CR3寄存器中
D4~D0：代表中断标志位对应的中断使能位在CRx寄存器的哪一位
D15~D8：代表中断标志位在SR寄存器中的哪一位

上面我们仅仅是给出了这个结论，其实仅仅是看上面的几行宏定义是看不出来各位代表什么意思的，只有从代码中推理出来，下面给出stm32f10x_usart.c中USART_GetITStatus函数的实现就可以推理出上面为什么将上面的那几个宏定义成那种形式了！
/**
* @brief Checks whether the specified USART interrupt has occurred or not.
* @param USARTx: Select the USART or the UART peripheral.
* This parameter can be one of the following values:
* USART1, USART2, USART3, UART4 or UART5.
* @param USART_IT: specifies the USART interrupt source to check.
* This parameter can be one of the following values:
* @arg USART_IT_CTS: CTS change interrupt (not available for UART4 and UART5)
* @arg USART_IT_LBD: LIN Break detection interrupt
* @arg USART_IT_TXE: Tansmit Data Register empty interrupt
* @arg USART_IT_TC: Transmission complete interrupt
* @arg USART_IT_RXNE: Receive Data register not empty interrupt
* @arg USART_IT_IDLE: Idle line detection interrupt
* @arg USART_IT_ORE: OverRun Error interrupt
* @arg USART_IT_NE: Noise Error interrupt
* @arg USART_IT_FE: Framing Error interrupt
* @arg USART_IT_PE: Parity Error interrupt
* @retval The new state of USART_IT (SET or RESET).
*/
ITStatus USART_GetITStatus(USART_TypeDef* USARTx, uint16_t USART_IT)
{
uint32_t bitpos = 0x00, itmask = 0x00, usartreg = 0x00;
ITStatus bitstatus = RESET;
/* Check the parameters */
assert_param(IS_USART_ALL_PERIPH(USARTx));
assert_param(IS_USART_GET_IT(USART_IT));
/* The CTS interrupt is not available for UART4 and UART5 */
if (USART_IT == USART_IT_CTS)
{
assert_param(IS_USART_123_PERIPH(USARTx));
}

/* Get the USART register index */
usartreg = (((uint8_t)USART_IT) >> 0x05); //由此可见D7~D5：代表中断标志位对应的中断使能位在
CR1、CR2还是CR3寄存器中
/* Get the interrupt position */
itmask = USART_IT & IT_Mask;
itmask = (uint32_t)0x01 << itmask; //由此可见D4~D0：代表中断标志位对应的中断使能位在CRx寄存器的哪一位

if (usartreg == 0x01) /* The IT is in CR1 register */
{
itmask &= USARTx->CR1;
}
else if (usartreg == 0x02) /* The IT is in CR2 register */
{
itmask &= USARTx->CR2;
}
else /* The IT is in CR3 register */
{
itmask &= USARTx->CR3;
}

bitpos = USART_IT >> 0x08; //由此可见D15~D8：代表中断标志位在SR寄存器中的哪一位
bitpos = (uint32_t)0x01 << bitpos;
bitpos &= USARTx->SR;
if ((itmask != (uint16_t)RESET)&&(bitpos != (uint16_t)RESET))
{
bitstatus = SET;
}
else
{
bitstatus = RESET;
}

return bitstatus;
}