Chapter 2. Programming Model
2-35
Instruction Set Summary
In general, oating-point word accesses should always be word-aligned and oating-point
double-word accesses should always be double-wordDaligned. Frequent use of misaligned
accesses is discouraged because they can degrade overall performance.
2.2.4 Floating-Point Operands
The MPC7400 provides hardware support for all single- and double-precision
oating-point operations for most value representations and all rounding modes. This
architecture provides for hardware to implement a oating-point system as deTned in
ANSI/IEEE standard 754-1985,
IEEE Standard for Binary Floating Point Arithmetic
.
Detailed information about the oating-point execution model can be found in Chapter 3,
òOperand Conventions,ó in
The Programming Environments Manual
.
The MPC7400 supports non-IEEE mode when FPSCR[29] is set. In this mode,
denormalized numbers are treated in a non-IEEE conforming manner. This is accomplished
by delivering results that are forced to the value zero.
2.3 Instruction Set Summary
This chapter describes instructions and addressing modes deTned for the MPC7400. These
instructions are divided into the following functional categories:
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Integer instructionsThese include arithmetic and logical instructions. For more
information, see Section 2.3.4.1, òInteger Instructions.ó
Floating-point instructionsThese include oating-point arithmetic instructions, as
well as instructions that affect the oating-point status and control register (FPSCR).
For more information, see Section 2.3.4.2, òFloating-Point Instructions.ó
Load and store instructionsThese include integer and oating-point load and store
instructions. For more information, see Section 2.3.4.3, òLoad and Store
Instructions.ó
Flow control instructionsThese include branching instructions, condition register
logical instructions, trap instructions, and other instructions that affect the
instruction ow. For more information, see Section 2.3.4.4, òBranch and Flow
Control Instructions.ó
Processor control instructionsThese instructions are used for synchronizing
memory accesses and managing caches, TLBs, and segment registers. For more
information, see Section 2.3.4.6, òProcessor Control InstructionsUISA,ó
Section 2.3.5.1, òProcessor Control InstructionsVEA,ó and Section 2.3.6.2,
òProcessor Control InstructionsOEA.ó
Memory synchronization instructionsThese instructions are used for memory
synchronizing. See Section 2.3.4.7, òMemory Synchronization
InstructionsUISA,ó and Section 2.3.5.2, òMemory Synchronization
InstructionsVEA,ó for more information.
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