1.1
Introduction to the Central Processing Unit (CPU)
1.2
Compatibility with the C28x Fixed-Point CPU
Program address bus (22)
Program data bus (32)
Read address bus (32)
Read data bus (32)
Write data bus (32)
Existing
memory,
peripherals,
interfaces
PIE
Write address bus (32)
LVF
LUF
C28x
+
FPU
Memory
bus
Memory
bus
Introduction to the Central Processing Unit (CPU)
www.ti.com
The C28x plus floating-point (C28x+FPU) processor extends the capabilities of the C28x fixed-point CPU
by adding registers and instructions to support IEEE single-precision floating point operations. This device
draws from the best features of digital signal processing; reduced instruction set computing (RISC); and
microcontroller architectures, firmware, and tool sets. The DSC features include a modified Harvard
architecture and circular addressing. The RISC features are single-cycle instruction execution,
register-to-register operations, and modified Harvard architecture (usable in Von Neumann mode). The
microcontroller features include ease of use through an intuitive instruction set, byte packing and
unpacking, and bit manipulation. The modified Harvard architecture of the CPU enables instruction and
data fetches to be performed in parallel. The CPU can read instructions and data while it writes data
simultaneously to maintain the single-cycle instruction operation across the pipeline. The CPU does this
over six separate address/data buses.
Throughout this document the following notations are used:
•
C28x refers to the C28x fixed-point CPU.
•
C28x plus Floating-Point and C28x+FPU both refer to the C28x CPU with enhancements to support
IEEE single-precision floating-point operations.
No changes have been made to the C28x base set of instructions, pipeline, or memory bus architecture.
Therefore, programs written for the C28x CPU are completely compatible with the C28x+FPU and all of
the features of the C28x documented in
TMS320C28x DSP CPU and Instruction Set Reference Guide
(literature number
) apply to the C28x+FPU.
shows basic functions of the FPU.
Figure 1-1. FPU Functional Block Diagram
8
Introduction
SPRUEO2A – June 2007 – Revised August 2008
Содержание TMS320C28 series
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