E300C3 Overview - Freescale Semiconductor MPC8313E Family Reference Manual

Chapter 7
e300 Processor Core Overview
This chapter provides an overview of features for the embedded microprocessors in the e300 core family,
which are PowerPC microprocessors built on Power Architecture technology. Throughout this chapter, the
terms 'e300 core', 'core', and 'processor' are used interchangeably. The term "e300c3" is used when
describing an implementation-specific feature or when a difference exists between different
configurations. The term 'e300' is used when describing a feature that pertains to the family of e300
processors. The MPC8313E uses an e300c3 core.
7.1

e300c3 Overview

This section describes the details of the e300 core, provides a block diagram showing the major functional
units, and briefly describes how these units interact. All differences between the e300 and previous
PowerPC implementations derived from the MPC603e processor are noted. For additional information,
refer to the e300 PowerPC Core Family Reference Manual.
The e300 core is a low-power implementation of this microprocessor family of reduced instruction set
computing (RISC) microprocessors. The core implements the 32-bit portion of the PowerPC architecture,
which defines 32-bit effective addresses, integer data types of 8, 16, and 32 bits, and floating-point data
types of 32 and 64 bits.
The core is a superscalar processor that can issue and retire as many as three instructions per clock cycle.
Instructions can execute out of program order for increased performance; however, the core makes
completion appear sequential.
The e300 core integrates independent execution units including: an integer unit (IU) a floating-point unit
(FPU), a branch processing unit (BPU), a load/store unit (LSU), and a system register unit (SRU). The
e300c3integrate an additional integer unit for a total of two IUs. The ability to execute instructions in
parallel and the use of simple instructions with rapid execution times yield high efficiency and throughput
for e300-core-based systems. Most integer instructions execute in one clock cycle. The additional IUs
along with enhanced multipliers in the e300c3improve multiply instructions to a maximum two-cycle
latency, a significant improvement from previous processors. In the e300c3 core, the FPU is pipelined so
a single-precision multiply-add instruction can be issued and completed every clock cycle. The
e300c3core provide hardware support for all single- and double-precision floating-point operations for
most value representations and all rounding modes.
Figure 7-1 shows a block diagram of the e300c3 core. Note that the e300c3 supports floating-point
operations and includes two integer units.
MPC8313E PowerQUICC II Pro Integrated Processor Family Reference Manual, Rev. 3
Freescale Semiconductor 7-1