Table of Contents
MSP430FR5969 Low Power Modes and Interrupts
Low Power Modes
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
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.