CC3000 Port and "__bic_SR_register"

Hi,

I'm trying to port the Basic WiFi to a PIC24 micro and I'm not familiar with the MSP430 architecture and the operation of interrupts.

Could someone please explain what the  "__bic_SR_register_on_exit(LPM3_bits);" portion of the code below does? I think it clears a bit on exit, but how does it stimulate something else to occur. This is from Board.c, line 237.

Regards,

James

// Timer A0 interrupt service routine
#pragma vector=TIMER1_A0_VECTOR
__interrupt void TIMER1_A0_ISR(void)
{
__bic_SR_register_on_exit(LPM3_bits);
__no_operation(); // For debugger
}