MSP 430 Problem #1: Interrupts A. Let us assume a P1.2 port pin is configured as

Question

MSP 430 Problem #1: Interrupts

A. Let us assume a P1.2 port pin is configured as an interrupt request input. Describe all steps involved in handling an interrupt request, from the moment a request is received (rising edge detected on P1.2) until the return from the corresponding interrupt handling routine. Be precise, and describe what is done in hardware and what is done in software.

B. What is interrupt nesting? Describe how the MSP430 deals with interrupt nesting.

C. What is interrupt selective masking? Describe how the MSP430 deals with selective masking.

D. What is the interrupt vector table? What is its content? How does it get initialized?

Explanation / Answer

B) Interrupt nesting is enabled if the GIE(general interrupt enable) bit is set inside an interrupt service routine. When interrupt nesting is enabled any interrupt occurring during an interrupt service routine will interrupt the routine, regardless of the interrupt pointers.

by Default the MSP430 clears the GIE(general interrupt enable) bit during the interrupt processing. so the programmer must explicitly enable nesting by setting the GIE bit in an interrupt service routine. In addition an individual masking bit must be set to allow the interrupts from the corresponding peripherals.

C) Maskable interrupts are caused by peripherals with interrupt capabalities, Each maskable interrupt sourse can be disabled individually by an interrupt enable bit(selective masking) or all maskable interrupts can be disabled by the GIE(general interrupt enable) bit in the status register.

MSP430: GIE in the status register

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