#### 6.57.17 MSP430 Built-in Functions

GCC provides a couple of special builtin functions to aid in the writing of interrupt handlers in C.

`__bic_SR_register_on_exit (int` mask`)`
  This clears the indicated bits in the saved copy of the status register currently residing on the stack. This only works inside interrupt handlers and the changes to the status register will only take affect once the handler returns.
`__bis_SR_register_on_exit (int` mask`)`
  This sets the indicated bits in the saved copy of the status register currently residing on the stack. This only works inside interrupt handlers and the changes to the status register will only take affect once the handler returns.