MC68030 Datasheet, PDF (363/602 Pages) Motorola, Inc – ENHANCED 32-BIT MICROPROCESSOR

Coprocessor Interface Description
The M68000 coprocessor interface also facilitates the design of coprocessors. The
coprocessor designer must only conform to the coprocessor interface and does not need an
extensive knowledge of the architecture of the main processor. Also, the main processor can
operate with a coprocessor without having explicit provisions made in the main processor
for the capabilities of that coprocessor. This provides a great deal of freedom in the
implementation of a given coprocessor.
10.1.2 Concurrent Operation Support
The programmer's model for the M68000 Family of microprocessors is based on sequential,
nonconcurrent instruction execution. This implies that the instructions in a given sequence
must appear to be executed in the order in which they occur. To maintain a uniform
programmer's model, any coprocessor extensions should also maintain the model of
sequential, nonconcurrent instruction execution at the user level. Consequently, the
programmer can assume that the images of registers and memory affected by a given
instruction have been updated when the next instruction in the sequence accessing these
registers or memory locations is executed.
The M68000 coprocessor interface provides full support of all operations necessary for
nonconcurrent operation of the main processor and its associated coprocessors. Although
the M68000 coprocessor interface allows concurrency in coprocessor execution, the
coprocessor designer is responsible for implementing this concurrency while maintaining a
programming model based on sequential nonconcurrent instruction execution.
For example, if the coprocessor determines that instruction “B” does not use or alter
resources to be altered or used by instruction “A”, instruction “B” can be executed
concurrently (if the execution hardware is also available). Thus, the required instruction
interdependencies and sequences of the program are always respected. The MC68882
coprocessor offers concurrent instruction execution while the MC68881 coprocessor does
not. However, the MC68030 can execute instructions concurrently with coprocessor
instruction execution in the MC68881.
MOTOROLA
MC68030 USER’S MANUAL
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