MAC7200 datasheet(390/976 Pages) FREESCALE

390 / 976 page

Initialization/Application Information

MAC7200 Microcontroller Family Reference Manual, Rev. 2

312

Freescale Semiconductor

The bulk of the interrupt service routine executes in segment E, with interrupts enabled.

Near the end of the service routine, the CPSR[F] flag is again set, disabling interrupt requests, and

preparing to perform the context switch.

At the end of segment F, the original value in the saved level mask (SLMASK) is restored to the current

level mask (CLMASK). Optionally, the service routine can directly load the CLMASK register with any

value with pending interrupt requests of certain levels need to be examined.

In segment G, the interrupt service routine completes execution. During this period of time (recall

interrupts are disabled in the CPSR), it is possible to access the interrupt controller to see if there are any

pending properly-enabled requests. Checking for any pending interrupt requests at this time provides the

ability to initiate processing of another interrupt without the need to return from the original ISR and then

incur the overhead of another interrupt exception.

At the conclusion of segment G, the processor core returns to the original interrupted task, or a different

task that is ready to execute.

MAC7200 Datasheet(PDF) 390 Page - Freescale Semiconductor, Inc