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MPC7400 RISC Microprocessor Users Manual
Instruction Set Summary
memory operands, see Chapter 3, òOperand Conventions,ó of
The Programming
Environments Manual
.
2.3.2.3 Effective Address Calculation
An effective address is the 32-bit sum computed by the processor when executing a
memory access or branch instruction or when fetching the next sequential instruction. For
a memory access instruction, if the sum of the effective address and the operand length
exceeds the maximum effective address, the memory operand is considered to wrap around
from the maximum effective address through effective address 0, as described in the
following paragraphs.
Effective address computations for both data and instruction accesses use 32-bit unsigned
binary arithmetic. A carry from bit 0 is ignored.
Load and store operations have the following modes of effective address generation:
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EA = (
r
A|0) + offset (including offset = 0) (register indirect with immediate index)
EA = (
r
A|0) +
r
B (register indirect with index)
Refer to Section 2.3.4.3.2, òInteger Load and Store Address Generation,ó for a detailed
description of effective address generation for load and store operations.
Branch instructions have three categories of effective address generation:
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Immediate
Link register indirect
Count register indirect
2.3.2.4 Synchronization
The synchronization described in this section refers to the state of the processor that is
performing the synchronization.
2.3.2.4.1 Context Synchronization
The System Call (
sc
) and Return from Interrupt (
rT
) instructions perform context
synchronization by allowing previously issued instructions to complete before performing
a change in context. Execution of one of these instructions ensures the following:
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No higher priority exception exists (
sc
).
All previous instructions have completed to a point where they can no longer cause
an exception. If a prior memory access instruction causes direct-store error
exceptions, the results are guaranteed to be determined before this instruction is
executed.