
MOTOROLA
Chapter 1. Overview
1-1
Chapter 1
Overview
This chapter provides an overview of features for the embedded G2 processor core, a
derivative of the original MPC603e PowerPC microprocessor design. The G2 core is an
implementation of the PowerPC microprocessor family. This reference manual also
describes the G2_LE core, which is a derivative of the G2 core The G2_LE core
implements some enhanced features with a true little-endian mode, an additional critical
interrupt signal, and four additional instruction BAT and four additional data BAT registers.
This document is written from the perspective of the G2 core and all of the descriptions
apply to both the G2 and G2_LE cores, except where explicitly noted. Note that throughout
this document, the terms G2 core, core, and processor are used interchangeably.
1.1
Overview
This section describes the details of the G2 core, provides a block diagram showing the
major functional units (see Figure 1-1), and briefly describes how these units interact. All
differences between the G2 and G2_LE implementations are noted.
The G2 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 G2 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 G2 core integrates five execution units—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 ability to execute five instructions in parallel and the use of simple instructions
with rapid execution times yield high efficiency and throughput for G2-core based systems.
Most integer instructions execute in one clock cycle. On the G2 core, the FPU is pipelined
so a single-precision multiply-add instruction can be issued and completed every clock
cycle. The G2 core provides hardware support for all single- and double-precision
floating-point operations for most value representations and all rounding modes.
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