
RCPU
REFERENCE MANUAL
ADDRESSING MODES AND INSTRUCTION SET SUMMARY
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MOTOROLA
4-1
SECTION 4
ADDRESSING MODES AND INSTRUCTION SET SUMMARY
This section describes instructions and address modes supported by the RCPU.
These instructions are divided into the following categories:
Integer instructions — These include computational and logical instructions.
Floating-point instructions — These include floating-point computational in-
structions, as well as instructions that affect the floating-point status and con-
trol register.
Load/store instructions — These include integer and floating-point load and
store instructions.
Flow control instruction — These include branching instructions, condition
register logical instructions, trap instructions, and other instructions that affect
the instruction flow.
Processor control instruction — These instructions are used to read from and
write to the condition register (CR), machine state register (MSR), and spe-
cial-purpose registers (SPRs), and to read from the time base register (TBU
or TBL).
Memory synchronization instructions — These instructions are used for syn-
chronizing memory.
Memory control instructions — These instructions provide control of the I-
cache.
Notice that this grouping of instructions does not necessarily indicate the execution
unit that processes a particular instruction or group of instructions. This information
is provided in
SECTION 9 INSTRUCTION SET
.
Integer instructions operate on byte, half-word, and word operands. Floating-point
instructions operate on single-precision and double-precision floating-point oper-
ands. The PowerPC architecture uses instructions that are four bytes long and
word-aligned. It provides for byte, half-word, and word operand fetches and stores
between memory and a set of 32 general-purpose registers (GPRs). It also pro-
vides for word and double-word operand fetches and stores between memory and
a set of 32 floating-point registers (FPRs).
Arithmetic and logical instructions do not modify memory. To use a memory oper-
and in a computation and then modify the same or another memory location, the
memory contents must be loaded into a register, modified, and then written back
to the target location.
4.1 Memory Addressing
A program references memory using the effective (logical) address computed by
the processor when it executes a load, store, branch, or cache instruction, and
when it fetches the next sequential instruction.
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