====== MSP430FR5969 Low Power Modes and Interrupts ======

===== Low Power Modes =====

{{ :microcontrollers:lpm1.png?direct&600 |}}

Low power modes can drastically reduce power consumption, going from around a hundred microamps in active mode to under a microamp (or tenths of a microamp) in the 3.x and 4.x low power modes.

==== LPMs in C ====

  * Use the following command to enter the x mode, where x = 0,1,2,3,4,3.5,or 4.5:
_bis_SR_register( GIE | LPMx_bits ); 
bis =  bit set 
  * To exit LPMx  use the following command inside the Interrupt Service Routine ISR, where x = 0,1,2,3,4,3.5,or 4.5 :
__bic_SR_register_on_exit(LPMx_bits ); 
 bic = bit clear

==== Low Power Implementation Notes ====

  * Choose the appropriate LPM that suits your application. For example, if you use the SPI communication, you need a clock. As result, you have to choose the LPM where the clock source for your SPI is enabled.
  * To support low power design, configure all unused pins as an input with pull down resistor to prevent them from floating.

===== Interrupts =====

==== Interrupt Priority ====

{{ :microcontrollers:interrupt1.png?direct&600 |}}
==== Interrupt Implementation Notes ====

  * Be aware of the interrupts priorities for the MCU that you are working on.
  * There are specific interruptible ports. Not all ports of the chip are interruptible.

**For port interrupts:**

  * If the interrupt will fire when the port status changed from Low to High, you should configure the port to be pulled down.
  * If the interrupt will fire when the port status changed from high to low, you should configure the port to be pulled up.

===== References =====

  * Interrupt : https://training.ti.com/msp430-workshop-series-5-12-interrupts?cu=1135311
  * Low-Power Optimization :  https://training.ti.com/msp430-workshop-series-7-12-low-power-optimization?cu=1135311