Question

In MSP430, interrupts are enabled/disabled by writing to the bit, called GIE, in the status register (SR: R2). Why do we use functions like below? Can’t we write the code directly in C?

_enable_interrupts();

_disable_interrupts();

Answer 1

-->we use interrrupts to wake the processor
-->setting low-power mode puts the micro controller "to sleep" so usually ,interrrupts would need ot be enabled as well.
-->_enable_interrupts() which enable the GIE bit present in SR register.
--->_disable_interrupts() to protect an atomic instruction sequence.Actually intrinsics don't need any declaration in
header files at all.They are know as compiler as IF and WHILE .
-->The header file is likely defining function prototypes for intrinsics from a different compiler,for portability .
-->Afer,all if an intrinsic isn't known to a compiler,you may provide an assembly funciton that implements it.
-->It is possible that comparable intrinsic but it has different name. like _disable_interrupt()

2)We cant directly write the code in C.because
-->The GIE SR bit in the MSP430 is generally not accessed using simple bitwise operator because there is no symbol defined in
C that represents the status register.
-->The compiler recognizes a number of intrinisic operators.Intrinsic are used like functions and produce assembly language
statements that would oterwise be inexpressed in c.
-->we can use C variables with this .
-->by including <msp430g2553.h> we can enable and disable functions.