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MPC603e & EC603e RISC Microprocessors User's Manual
MOTOROLA
An attempt to execute an illegal instruction invokes the illegal instruction error handler (a
program exception) but has no other effect. See Section 4.5.7, “Program Exception
(0x00700),” for additional information about illegal and invalid instruction exceptions.
With the exception of the instruction consisting entirely of binary zeros, the illegal
instructions are available for further additions to the PowerPC architecture.
2.3.1.4 Reserved Instruction Class
Reserved instructions are allocated to specific implementation-dependent purposes not
defined by the PowerPC architecture. An attempt to execute an unimplemented reserved
instruction invokes the illegal instruction error handler (a program exception). See
Section 4.5.7, “Program Exception (0x00700),” for additional information about illegal and
invalid instruction exceptions.
The following types of instructions are included in this class:
Implementation-specific instructions (for example, Load Data TLB Entry (
tlbld
)
and Load Instruction TLB Entry (
tlbli
) instructions)
Optional instructions defined by the PowerPC architecture but not implemented by
the 603e (for example, Floating Square Root (
fsqrt
) and Floating Square Root
Single (
fsqrts
) instructions)
2.3.2 Addressing Modes
This section provides an overview of conventions for addressing memory and for
calculating effective addresses as defined by the PowerPC architecture for 32-bit
implementations. For more detailed information, see “Conventions,” in Chapter 4,
“Addressing Modes and Instruction Set Summary,” of
The Programming Environments
Manual
.
2.3.2.1 Memory Addressing
A program references memory using the effective (logical) address computed by the
processor when it executes a memory access or branch instruction or when it fetches the
next sequential instruction.
2.3.2.2 Memory Operands
Bytes in memory are numbered consecutively starting with zero. Each number is the
address of the corresponding byte.
Memory operands may be bytes, half words, words, or double words, or, for the load/store
multiple and load/store string instructions, a sequence of bytes or words. The address of a
memory operand is the address of its first byte (that is, of its lowest-numbered byte).
Operand length is implicit for each instruction. The PowerPC architecture supports both
big-endian and little-endian byte ordering. The default byte and bit ordering is big-endian.
See “Byte Ordering” in Chapter 3, “Operand Conventions,” in
The Programming