Epic Unit Overview - Motorola MPC8240 User Manual

Chapter 11
Embedded Programmable Interrupt
Controller (EPIC) Unit
This chapter describes the embedded programmable interrupt controller (EPIC) interrupt
protocol, the various types of interrupt sources controlled by the EPIC unit, and a complete
description of the EPIC registers with some programming guidelines.
The interrupt sources and soft reset controlled by the EPIC unit, the sreset signal, and the
internal mcp generated by the MPC8240 central control unit (CCU) all cause exceptions in
the processor core. The int signal is the main interrupt output from the EPIC to the
processor core and causes the external interrupt exception. The external SRESET signal or
the internal sreset output of the EPIC unit cause the soft reset processor exception. The
machine check exception is caused by the internal mcp signal generated by the CCU,
informing the processor of error conditions, the assertion of the external NMI signal, and
other conditions. See Chapter 13, "Error Handling," for further information on the sources
of the internal mcp signal.

11.1 EPIC Unit Overview

The EPIC unit implements the necessary functions to provide a flexible and
general-purpose interrupt controller solution. The EPIC pools hardware-generated
interrupts from many sources, both within the MPC8240 and externally, and delivers them
to the processor core in a prioritized manner. Note that the assertion of the INTA signal to
the PCI bus is managed by the messaging unit (MU).
The EPIC solution adopts the OpenPIC architecture (architecture developed jointly by
AMD and Cyrix for SMP interrupt solutions) and implements the logic and programming
structures according to that specification. The MPC8240's EPIC unit supports up to five
external interrupts or one serial-style interrupt line (supporting 16 interrupts) and a
pass-through mode. Additionally, the EPIC unit supports four internal logic-driven
interrupts and four timers with interrupts. The following sections give an overview of the
features of the EPIC unit and a complete summary of the signals used by the EPIC unit.
Chapter 11. Embedded Programmable Interrupt Controller (EPIC) Unit 11-1