The Proper place to use the volatile keyword?

Answer:

A volatile is an important qualifier in C programming. Here I am pointing some places where we need to use the volatile keyword.

• Accessing the memory-mapped peripherals register or hardware status register.

#define COM_STATUS_BIT  0x00000006
uint32_t const volatile * const pStatusReg = (uint32_t*)0x00020000;
unit32_t GetRecvData()
{
    unit32_t RecvData;
    
    //Code to receive data
    while (((*pStatusReg)  & COM_STATUS_BIT) == 0)
    {
        // Wait until flag does not set
        //Received data in RecvData
    }
    return RecvData;
}

• Sharing the global variables or buffers between the multiple threads.
• Accessing the global variables in an interrupt routine or signal handler.

volatile int giFlag = 0;
ISR(void)
{
    giFlag = 1;
}
int main(void)
{
    while (!giFlag)
    {
        //do some work
    }
    return 0;
}