Principles for Low-Power Applications
2-16 System Resets, Interrupts, and Operating Modes
2.4 Principles for Low-Power Applications
Often, the most important factor for reducing power consumption is using the
MSP430s clock system to maximize the time in LPM3. LPM3 power
consumption is less than 2 µA typical with both a real-time clock function and
all interrupts active. A 32-kHz watch crystal is used for the ACLK and the CPU
is clocked from the DCO (normally off) which has a 6-µs wake-up.
-Use interrupts to wake the processor and control program flow.
-Peripherals should be switched on only when needed.
-Use low-power integrated peripheral modules in place of software driven
functions. For example Timer_A and Timer_B can automatically generate
PWM and capture external timing, with no CPU resources.
-Calculated branching and fast table look-ups should be used in place of
flag polling and long software calculations.
-Avoid frequent subroutine and function calls due to overhead.
-For longer software routines, single-cycle CPU registers should be used.
2.5 Connection of Unused Pins
The correct termination of all unused pins is listed in Table 22.

Table 22.Connection of Unused Pins

Pin Potential Comment
AVCC DVCC
AVSS DVSS
VREF+ Open
VeREF+ DVSS
VREF−/VeREF− DVSS
XIN DVCC
XOUT Open
XT2IN DVSS 43x and 44x devices
XT2OUT Open 43x and 44x devices
Px.0 to Px.7 Open Switched to port function, output direction
RST/NMI DVCC or VCC 47 k pullup with 10nF pull down
R03 DVSS
COM0 Open
TDO Open
TDI Open
TMS Open
TCK Open
Sxx Open