addressing modes of the MPU. Some addressing modes are
restricted
for some instructions
in keeping with the M68000 Family architectural definitions (e.g., program counter relative
addressing is not allowed for a destination operand).
The orthogonal instruction set of the FPCP, along with the flexible branches and addressing
modes of the MPU, allows a programmer or a compiler writer to think of the FPCP as
though it were part of the MPU. There are no special restrictions imposed by the copro-
cessor interface, and floating-point arithmetic is coded exactly like integer arithmetic.
1.6 MC68882 PROGRAMMING CONSIDERATIONS
To exploit the enhanced performance of the MC68882 requires the programmer to be aware
of the manner in which the coprocessor overlaps execution of instructions. Upgrading a
system to use the MC68882 requires minor system software changes but no user software
changes. To optimize applications code for the MC68882 may require reordering of floating-
point instructions. SECTION 5 COPROCESSOR PROGRAMMING describes the concurrency
capabilities of the MC68882, the required system software changes, and the optimization
of existing software for the enhanced floating-point coprocessor.
FREESCALE
1-16
MC68881/MC68882 USER'S MANUAL
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