
RCPU
REFERENCE MANUAL
INSTRUCTION CACHE
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MOTOROLA
5-9
5.4.4 Unlock Line
The
unlock line
operation is used to unlock locked cache lines. The
unlock line
operation is performed on a single cache line. If the line is found in the cache
(cache hit), it is unlocked and starts to operate as a regular valid cache line. If the
line is not found in the cache (cache miss), no operation is performed, and the com-
mand terminates with no exception.
The following sequence unlocks one cache line:
1. Write the address of the line to be unlocked to the ICADR
2. Set the
unlock line
command in the ICCST
This command has no error cases that the user needs to check.
The I-cache performs this instruction in one clock cycle. To calculate the latency of
this instruction accurately, bus latency should be taken into account.
5.4.5 Unlock All
The
unlock all
operation is used to unlock the whole cache. This operation is per-
formed on all cache lines. If a line is locked it is unlocked and starts to operate as
a regular valid cache line. If a line is not locked or if it is invalid no operation is per-
formed.
In order to unlock the whole cache set the
unlock all
command in the ICCST.
This command has no error cases that the user needs to check.
The I-cache performs this instruction in one clock cycle. To calculate the latency of
this instruction accurately, bus latency should be taken into account.
5.4.6 Cache Enable
To enable the cache, set the
cache enable
command in the ICCST. This operation
can be performed only at the supervisor privilege level. The
cache enable
com-
mand has no error cases that the user needs to check.
5.4.7 Cache Disable
To disable the cache, set the
cache disable
command in the ICCST. This opera-
tion can be performed only at the supervisor privilege level. The cache disable
command has no error cases that the user needs to check.
5.4.8 Cache Inhibit
A memory region can be programmed in the chip select logic to be cache inhibited.
When an instruction is fetched from a cache-inhibited region, the full line is brought
to the internal burst buffer. Instructions stored in the burst buffer that originated
from a cache-inhibited region may be sent to the processor no more than once be-
fore being re-fetched.
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