Overview

5.1 Overview

Typically, DSPs work in an environment that contains multiple external asynchronous events. These events require tasks to be performed by the DSP when they occur. An interrupt is an event that stops the current process in the CPU so that the CPU can attend to the task needing completion because of the event. These interrupt sources can be on chip or off chip, such as timers, analog-to-digital converters, or other peripherals.

Servicing an interrupt involves saving the context of the current process, com- pleting the interrupt task, restoring the registers and the process context, and resuming the original process. There are eight registers that control servicing interrupts.

An appropriate transition on an interrupt pin sets the pending status of the interrupt within the interrupt flag register (IFR). If the interrupt is properly enabled, the CPU begins processing the interrupt and redirecting program flow to the interrupt service routine.

5.1.1Types of Interrupts and Signals Used

There are three types of interrupts on the CPUs of the TMS320C6000DSPs.

-Reset

-Maskable

-Nonmaskable

These three types are differentiated by their priorities, as shown in Table 5−1. The reset interrupt has the highest priority and corresponds to the RESET signal. The nonmaskable interrupt has the second highest priority and corresponds to the NMI signal. The lowest priority interrupts are interrupts 4−15 corresponding to the INT4−INT15 signals. RESET, NMI, and some of the INT4−INT15 signals are mapped to pins on C6000 devices. Some of the INT4−INT15 interrupt signals are used by internal peripherals and some may be unavailable or can be used under software control. Check your device- specific data manual to see your interrupt specifications.

5-2

Interrupts

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Texas Instruments TMS320C67X/C67X+ DSP manual Overview, Types of Interrupts and Signals Used