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Microcontroller Programming and Interfacing Texas Instruments MSP430 by Daniel J. Pack, Steven F. Barrett

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CHAPTER 7
Resets and Interrupts
Objectives: After reading this chapter, the reader should be able to
Describe MSP430 resets and their functions
Explain the general concept of and the need for interrupts
Describe in general terms the steps required to implement an interrupt service routine
Identify MSP430 microcontroller maskable and non-maskable interrupts
Illustrate how the priority among resets and interrupts are determined in the MSP430 micro-
controller
Explain the process to identify the source of resets and interrupts
Describe the process to service interrupts
Properly configure the MSP430 microcontroller and write interrupt service routines to respond
to interrupts
In computer operation, there is a need to bring the computer back to a known state due to
program or system errors or simply because it serves the purpose of an application at hand. Bringing
the computer back to a known state involves re-initializing registers, executing start up instructions,
and setting up peripheral devices, including input and output systems, to default states. This process
and the source that caused the process is called a reset. In other applications, there is a need to stop
executing the current task and taking care of an urgent request made by internal devices, external
signals, or the result of the current or other software programs. These requests are called interrupts.
Resets and interrupts are closely related. In fact, the process of bringing the computer back to a
known state and performing an unplanned service as a response to an urgent request is almost
identical as we will see in this chapter.
7.1 MOTIVAT ION
One of the primary reasons to use MSP430 microcontrollers is an ability to minimize power usage
by allowing programmers to configure the microcontroller to run with different operational modes
based on the environmental factors or timed events. The subject of this chapter is the means of the
controller to implement mechanisms to switch between two or more different power consumption

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