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Operating Modes
1.4
Operating Modes
The MSP430 family is designed for ultralow-power applications and uses different operating modes shown
in
The operating modes take into account three different needs:
•
Ultra-low power
•
Speed and data throughput
•
Minimization of individual peripheral current consumption
The low-power modes LPM0 through LPM4 are configured with the CPUOFF, OSCOFF, SCG0, and
SCG1 bits in the SR. The advantage of including the CPUOFF, OSCOFF, SCG0, and SCG1 mode-control
bits in the SR is that the present operating mode is saved onto the stack during an interrupt service
routine. Program flow returns to the previous operating mode if the saved SR value is not altered during
the interrupt service routine. Program flow can be returned to a different operating mode by manipulating
the saved SR value on the stack inside of the interrupt service routine. When setting any of the mode-
control bits, the selected operating mode takes effect immediately. Peripherals operating with any disabled
clock are disabled until the clock becomes active. Peripherals may also be disabled with their individual
control register settings. All I/O port pins, RAM, and registers are unchanged. Wakeup from LPM0 through
LPM4 is possible through all enabled interrupts.
When LPMx.5 (LPM3.5 or LPM4.5) is entered, the voltage regulator of the Power Management Module
(PMM) is disabled. All RAM and register contents are lost. Although the I/O register contents are lost, the
I/O pin states are locked upon LPMx.5 entry. See the
chapter for further details. Wakeup from
LPM4.5 is possible via a power sequence, a RST event, or from specific I/O. Wakeup from LPM3.5 is
possible via a power sequence, a RST event, RTC event, or from specific I/O.
NOTE:
The TEST/SBWTCK pin is used for interfacing to the development tools via Spy-Bi-Wire and
JTAG. When the TEST/SBWTCK pin is high, wakeup times from LPM2, LPM3, and LPM4
may be different compared to when TEST/SBWTCK is low. Pay careful attention to the real-
time behavior when exiting from LPM2, LPM3, and LPM4 with the device connected to a
development tool (for example, MSP-FET430UIF). See the
chapter for further
details.
35
SLAU272C – May 2011 – Revised November 2013
System Resets, Interrupts, and Operating Modes, System Control Module
(SYS)
Copyright © 2011–2013, Texas Instruments Incorporated