MC68030 Datasheet, PDF (361/602 Pages) Motorola, Inc – ENHANCED 32-BIT MICROPROCESSOR

SECTION 10
COPROCESSOR INTERFACE DESCRIPTION
The M68000 Family of general-purpose microprocessors provides a level of performance
that satisfies a wide range of computer applications. Special-purpose hardware, however,
can often provide a higher level of performance for a specific application. The coprocessor
concept allows the capabilities and performance of a general-purpose processor to be
enhanced for a particular application without encumbering the main processor architecture.
A coprocessor can efficiently meet specific capability requirements that must typically be
implemented in software by a general-purpose processor. With a general-purpose main
processor and the appropriate coprocessor(s), the processing capabilities of a system can
be tailored to a specific application.
The MC68030 supports the M68000 coprocessor interface described in this section. The
section is intended for designers who are implementing coprocessors to interface with the
MC68030.
The designer of a system that uses one or more Motorola coprocessors (the MC68881 or
MC68882 floating-point coprocessor, for example) does not require a detailed knowledge of
the M68000 coprocessor interface. Motorola coprocessors conform to the interface
described in this section. Typically, they implement a subset of the interface, and that subset
is described in the coprocessor user's manual. These coprocessors execute Motorola
defined instructions that are described in the user's manual for each coprocessor.
10.1 INTRODUCTION
The distinction between standard peripheral hardware and a M68000 coprocessor is
important from a perspective of the programming model. The programming model of the
main processor consists of the instruction set, register set, and memory map available to the
programmer. An M68000 coprocessor is a device or set of devices that communicates with
the main processor through the protocol defined as the M68000 coprocessor interface. The
programming model for a coprocessor is different than that for a peripheral device. A
coprocessor adds additional instructions and generally additional registers and data types
to the programming model that are not directly supported by the main processor
architecture. The additional instructions are dedicated coprocessor instructions that utilize
the coprocessor capabilities. The necessary interactions between the main processor and
the coprocessor that provide a given service are transparent to the programmer. That is, the
programmer does not need to know the specific communication protocol between the main
processor and the coprocessor because this protocol is implemented in hardware. Thus, the
coprocessor can provide capabilities to the user without appearing separate from the main
processor.
MOTOROLA
MC68030 USER’S MANUAL
10-1