How Interrupts Work
Interrupt Vector Table – How is it different than other MCU’s?
The MSP430 Vector Table is similar and dissimilar to other microcontrollers:
• The MSP430, like most microcontrollers, uses an Interrupt Vector Table. This is an area
of memory that specifies a vector (i.e. ISR address) for each interrupt source.
• Some processors provide a unique ISR (and thus, vector) for every interrupt source.
Other processors provide only 1 interrupt vector and make the user program figure which
interrupt occurred. To maximize flexibility and minimize cost and power, the MSP430 falls
in between these two extremes. There are some interrupts which have their own,
dedicated interrupt vector – while other interrupts are logically grouped together.
• Where the MSP430 differs from many other processors is that it includes an Interrupt
Vector (IV) register for each grouped interrupt; reading this register returns the highest-
priority, enabled interrupt for that group of interrupt sources. As we’ll see later in this
chapter, all you need to do is read this register to quickly determine which specific
interrupt to handle.
Note: We’ll describe Interrupt Vector Table in more detail later in the chapter.
MSP430 Workshop - Interrupts 5 - 13
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