Motorola MPC8240 User Manual page 620

Cache block. The cacheable unit for a PowerPC processor. The size of a
Cache coherency. Caches are coherent if a processor performing a read from
Cast-outs. Cache block that must be written to memory when a snoop miss
Context synchronization. Context synchronization is the result of specific
Copy-back operation. A cache operation in which a cache line is copied
D
Denormalized number. A nonzero floating-point number whose exponent
Direct-store segment access. An access to an I/O address space. The 603
E
Exception. An unusual or error condition encountered by the processor that
Exception handler. A software routine that executes when an exception
Glossary-2
cache block may vary among processors. For the 603e, it is one
cache line (8 words).
its cache is supplied with data corresponding to the most recent value
written to memory or to another processor's cache.
causes the least recently used block with modified data to be
replaced.
instructions (such as sc or rfi) or when certain events occur (such as
an exception). During context synchronization, all instructions in
execution complete past the point where they can produce an
exception; all instructions in execution complete in the context in
which they began execution; all subsequent instructions are fetched
and executed in the new context.
back to memory to enforce cache coherency. Copy-back operations
consist of snoop push-out operations and cache cast-out operations.
has a reserved value, usually the format's minimum, and whose
explicit or implicit leading significand bit is zero.
defines separate memory-mapped and I/O address spaces, or
segments, distinguished by the corresponding segment register T bit
in the address translation logic of the 603. If the T bit is cleared, the
memory reference is a normal memory-mapped access and can use
the virtual memory management hardware of the 603. If the T bit is
set, the memory reference is a direct-store access.
results in special processing.
occurs. Normally, the exception handler corrects the condition that
caused the exception, or performs some other meaningful task (such
as aborting the program that caused the exception). The addresses of
the exception handlers are defined by a two-word exception vector
that is branched to automatically when an exception occurs.
MPC8240 Integrated Processor User's Manual