Freescale Semiconductor SC140 specifications Instruction Set Accelerator Plug-In, Introduction

Chapter 6 Instruction Set Accelerator Plug-In

This chapter describes the ISAP capability of the SC140 core, and how to incorporate an ISAP when using the SC140 core as part of a larger system.

6.1 Introduction

An ISAP is an Instruction Set Accelerator Plug-in- a unit external to the core that the SC140 core controls using dedicated instructions that are incorporated into the SC140 program. The SC140 has an interface and dedicated encoding space that enables defining and integrating such a unit.

The ISAP enables you to enhance the core instruction set with additional application-specific instructions that are not part of the original SC140 instruction set. For example, ISAPs could enhance the SC140 to support floating-point arithmetic, image processing capabilities, etc.

ISAP support is integral to the SC140 development tools, so the SC140 assembler, simulator and compiler can all be modularly configured to support the specific ISAP(s) definition. This enables the programmer to effectively use ISAP instructions in the source code like any other SC140 instruction (with minor modifications). However, the specific ISAP instruction set and programming rules are specific to each ISAP and are out of the scope of this document.

Single or multiple ISAPs can be connected to a single SC140 core. The normal configuration is of instructions being dispatched to one ISAP at a time. 1

An ISAP normally has its own set of registers, by which it can exchange data with the core or data memory, as well as execute data processing instructions.

1.However, using the SIMD (single instruction, multiple data) approach, more complex configurations that enable dispatching an instruction to more than one ISAP at a time are possible. For details, see the Integration Guide.

SC140 DSP Core Reference Manual 6-57