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Chapter 6
Instruction Cache
Preliminary User’s Manual U15839EE1V0UM00
(5)
Autofill Function (Way 0 only)
The autofill function automatically fills instructions for one way. Once autofilled, a way is automati-
cally locked and write is disabled and it operates the same as a ROM that is accessible in one
cycle. When the lock is released, it again operates as an instruction cache.
Instruction cache autofill performs the following procedure:
(1)
Clear (invalidate) the tags of way 0 (see “Tag Clear Function” on page 163).
(2)
Set the address corresponding to the memory area to be autofilled in the instruction cache
data configuration register (ICD).
(3)
Branch to the cacheable area corresponding to the tag information set in the ICD register.
(4)
Set bit 4 (FILL0) of the instruction cache control register (ICC).
(5)
When autofill is complete, bit 12 (LOCK0) of the ICC register is automatically set “1” and the
way 0 is locked. At that same time, read bit FILL0 of the ICC register and confirm that bit is
cleared “0”.
Remarks: 1. A lock is released by clearing bit LOCK0 of the ICC register.
2. While the iCache autofill operation is ongoing, neither interrupt nor NMI will be served
by CPU until the iCache autofill procedure is finished. Even for the situation that a
required interrupt service function is by chance already available in the second way of
iCache, CPU can not access these opcodes until the autofill operation of the iCache
way 0 is completed. Direct opcode execution from the VSB is also not possible in gen-
eral during the processing time of the autofill operation.
3. Since the autofill operation is performed from the external memory to the instruction
cache via the VSB, other processing can be performed at the same time, but only if the
processing involves operations within the CPU (processing without any VSB and NPB
accesses).
Caution:
Run the code to perform the above operations from the memory areas shown below:
•
(1), (2), (3)......... Uncacheable area
•
(4)..................... Cacheable area. If bit 4 (FILL0) of the ICC register is set
using an uncacheable area, autofill cannot be performed (invalid operation).
•
(5)..................... Either a cacheable area or an uncacheable area
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