
MOTOROLA
Glossary of Terms and Abbreviations
For More Information On This Product,
Go to: www.freescale.com
Glossary-3
Bus clock.
Clock that causes the bus state transitions.
Bus master.
The owner of the address or data bus; the device that initiates
or requests the transaction.
C
Cache.
High-speed memory containing recently accessed data or
instructions (subset of main memory).
Cache block.
A small region of contiguous memory that is copied from
memory into a
cache
. The size of a
cache
block
may vary among
processors; the maximum block size is one
page
. In PowerPC
processors,
cache coherency
is maintained on a cache-block basis.
Note that the term
cache
block
is often used interchangeably with
‘cache line.’
Cache coherency.
An attribute wherein an accurate and common view of
memory is provided to all devices that share the same memory
system. Caches are coherent if a processor performing a read from
its cache is supplied with data corresponding to the most recent value
written to memory or to another processor’s cache.
Cache flush.
An operation that removes from a cache any data from a
specified address range. This operation ensures that any modified
data within the specified address range is written back to main
memory. This operation is generated typically by a Data Cache
Block Flush (
dcbf
) instruction.
Caching-inhibited.
A memory update policy in which the cache is bypassed
and the load or store is performed to or from main memory.
Cast out.
A
cache block
that must be written to memory when a cache miss
causes a
cache
block
to be replaced.
Changed bit.
One of two
page history bits
found in each
page table entry
(PTE). The processor sets the changed bit if any store is performed
into the
page
. See also
Page access history bits
and
Referenced bit
.
Clean.
An operation that causes a
cache
block
to be written to memory, if
modified, and then left in a valid, unmodified state in the cache.
Clear.
To cause a bit or bit field to register a value of zero. See also
Set
.
Completion.
Completion occurs when an instruction has finished executing,
written back any results, and is removed from the completion queue
(CQ). When an instruction completes, it is guaranteed that this
instruction and all previous instructions can cause no exceptions.
F
Freescale Semiconductor, Inc.
n
.