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Chapter 6
Instruction Cache
Preliminary User’s Manual U15839EE1V0UM00
(4)
Tag Clear Function
The tag clear function clears (invalidates) the tags of one way. In addition, it automatically clears
(invalidates) the tags of all ways on a system reset. Instruction cache tag clear performs the follow-
ing procedure:
(1)
Read the instruction cache control register (ICC) and confirm that bits 0 and 1 (TCLR0,
TCLR1) are all cleared.
(2)
Read the ICC register and confirm that bit 12 (LOCK0) is cleared
(3)
Set bit TCLR0 or bit TCLR1 of the ICC register as follows:
Cautions: 1. To clear the instruction cache tags, the tag clear operation by setting the bits
TCLR0 or TCLR1 of the ICC register must be executed twice.
2. Perform all of (1) to (3) above (tag clear) executing the code in an uncacheable
area (tags are not cleared if the above processing is performed by code in a
cacheable area).
•
When clearing way 0 and way 1 at the same time:
(a) Set the TCLR0 and TCLR1 bits.
(b) Read the TCLR0 and TCLR1 bits to confirm that these bits are cleared.
(c) Perform (a) and (b) above again.
•
When clearing way 0 and way 1 individually
Note
:
(a) Set the TCLR0 bit.
(b) Read the TCLR0 bit to confirm that this bit is cleared.
(c) Perform (a) and (b) above again.
(d) Set the TCLR1 bit.
(e) Read the TCLR1 bit to confirm that this bit is cleared.
(f) Perform (d) and (e) above again.
Note: The setting can also be made in order of (d)-(e)-(f)-(a)-(b)-(c).
3. Way 0 shares the counter to clear tags with way 1.
Therefore a clear tag operation must not be started (set the TCLR0 bit or TCLR1
bit of the ICC register), even if the other way is currently being cleared. When
clearing the tags of way 0 and way 1 individually, if tag clearing for either way is
executed during tag clear execution for the other way (TCLR0 or TCLR1 = “1”),
the counter stops in the middle of tag clearing. Consequently, normal tag clearing
cannot be performed because the counter switches to perform the other tag clear
operation still indicating the value it had when stopped halfway. Be sure to con-
firm that tag clearing for one way is completed (TCLR0 or TCLR1 = “0”) before
performing tag clearing for the other way.
When setting both bits at the same time as shown below, normal tag clearing will
be performed properly.
4. Be sure not to perform other processing simultaneously with tag clearing before
reading the TCLR0 and TCLR1 bits of the ICC register and confirming that these
bits are cleared “0”.
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