title: interrupt flag vs interrupt pending bit stm32
body: <p>I'm using the <code>std</code> library. I don't know what the difference between <code>I2C_FLAG_TXE</code> and <code>I2C_IT_TXE</code> is.</p>
  
  <p>Why when in interrupt function we don't use <code>I2C_ClearFlag</code> instead <code>I2C_ClearITPendingBit</code>? When do we used <code>I2C_ClearFlag</code>? </p>
  
  <p>I'm starting learn <code>stm32f4</code>. I have very little experience.</p>