Freescale Semiconductor MPC5604B - Introduction

MPC5604B/C Microcontroller Reference Manual, Rev. 8
Freescale Semiconductor 269
Chapter 16
Interrupt Controller (INTC)
16.1 Introduction
The INTC provides priority-based preemptive scheduling of interrupt service requests (ISRs). This
scheduling scheme is suitable for statically scheduled hard real-time systems. The INTC supports 142
interrupt requests. It is targeted to work with a Power Architecture technology processor and automotive
powertrain applications where the ISRs nest to multiple levels, but it also can be used with other processors
and applications.
For high priority interrupt requests in these target applications, the time from the assertion of the
peripheral’s interrupt request from the peripheral to when the processor is performing useful work to
service the interrupt request needs to be minimized. The INTC supports this goal by providing a unique
vector for each interrupt request source. It also provides 16 priorities so that lower priority ISRs do not
delay the execution of higher priority ISRs. Since each individual application will have different priorities
for each source of interrupt request, the priority of each interrupt request is configurable.
When multiple tasks share a resource, coherent accesses to that resource need to be supported. The INTC
supports the priority ceiling protocol for coherent accesses. By providing a modifiable priority mask, the
priority can be raised temporarily so that all tasks which share the resource cannot preempt each other.
Multiple processors can assert interrupt requests to each other through software configurable interrupt
requests. These same software configurable interrupt requests also can be used to break the work involved
in servicing an interrupt request into a high priority portion and a low priority portion. The high priority
portion is initiated by a peripheral interrupt request, but then the ISR can assert a software configurable
interrupt request to finish the servicing in a lower priority ISR. Therefore these software configurable
interrupt requests can be used instead of the peripheral ISR scheduling a task through the RTOS.
16.2 Features
• Supports 134 peripheral and 8 software-configurable interrupt request sources
• Unique 9-bit vector per interrupt source
• Each interrupt source can be programmed to one of 16 priorities
• Preemption
— Preemptive prioritized interrupt requests to processor
— ISR at a higher priority preempts ISRs or tasks at lower priorities
— Automatic pushing or popping of preempted priority to or from a LIFO
— Ability to modify the ISR or task priority; modifying the priority can be used to implement the
priority ceiling protocol for accessing shared resources.
• Low latency – 3 clocks from receipt of interrupt request from peripheral to interrupt request to
processor