Btb Control; Disabling/Enabling; Invalidation - Intel XScale Core Developer's Manual

5.2

BTB Control

5.2.1

Disabling/Enabling

The BTB is always disabled with Reset. Software can enable the BTB through a bit in a
coprocessor register (see
Before enabling or disabling the BTB, software must invalidate it (described in the following
section). This action will ensure correct operation in case stale data is in the BTB. Software should
not place any branch instruction between the code that invalidates the BTB and the code that
enables/disables it.
5.2.2

Invalidation

There are four ways the contents of the BTB can be invalidated.
1. Reset
2. Software can directly invalidate the BTB via a CP15, register 7 function. Refer to
Section 7.2.8, "Register 7: Cache Functions" on page
3. The BTB is invalidated when the Process ID Register is written.
4. The BTB is invalidated when the instruction cache is invalidated via CP15, register 7
functions.
Developer's Manual
Section 7.2.2).
January, 2004
Intel XScale® Core Developer's Manual
Branch Target Buffer
7-87.
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