SC667201MMG3 datasheet(11/120 Pages) FREESCALE

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MPC5642A Microcontroller Data Sheet, Rev. 3.1

Freescale Semiconductor

Introduction

1.5.4

Interrupt controller (INTC)

The INTC provides priority-based preemptive scheduling of interrupt requests, suitable for statically scheduled hard real-time

systems.

For high priority interrupt requests, the time from the assertion of the interrupt request from the peripheral to when the processor

is executing the interrupt service routine (ISR) has been minimized. The INTC provides a unique vector for each interrupt

request source for quick determination of which ISR needs to be executed. It also provides an ample number of priorities so that

lower priority ISRs do not delay the execution of higher priority ISRs. To allow the appropriate priorities for each source of

interrupt request, the priority of each interrupt request is software 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.

The INTC provides the following features:

•

9-bit vector addresses

•

Unique vector for each interrupt request source

•

Hardware connection to processor or read from register

•

Each interrupt source can assigned a specific priority by software

•

Preemptive prioritized interrupt requests to processor

•

ISR at a higher priority preempts executing 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 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

This device also includes a non-maskable interrupt (NMI) pin that bypasses the INTC and multiplexing logic.

1.5.5

Memory protection unit (MPU)

The Memory Protection Unit (MPU) provides hardware access control for all memory references generated in a device. Using

preprogrammed region descriptors, which define memory spaces and their associated access rights, the MPU concurrently

monitors all system bus transactions and evaluates the appropriateness of each transfer. Memory references with sufficient

access control rights are allowed to complete; references that are not mapped to any region descriptor or have insufficient rights

are terminated with a protection error response.

The MPU has these major features:

•

Support for 16 memory region descriptors, each 128 bits in size

— Specification of start and end addresses provide granularity for region sizes from 32 bytes to 4 GB

— MPU is invalid at reset, thus no access restrictions are enforced

— 2 types of access control definitions: processor core bus master supports the traditional {read, write, execute}

permissions with independent definitions for supervisor and user mode accesses; the remaining non-core bus

masters (eDMA, FlexRay) support {read, write} attributes

— Automatic hardware maintenance of the region descriptor valid bit removes issues associated with maintaining a

coherent image of the descriptor

— Alternate memory view of the access control word for each descriptor provides an efficient mechanism to

dynamically alter the access rights of a descriptor only

— For overlapping region descriptors, priority is given to permission granting over access denying as this approach

provides more flexibility to system software

•

Support for two XBAR slave port connections (SRAM and PBRIDGE)

— For each connected XBAR slave port (SRAM and PBRIDGE), MPU hardware monitors every port access using

the preprogrammed memory region descriptors

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