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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
August 2006
Developer’s Manual
Order Number: 306262-004US
73
Intel XScale
®
Processor—Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
3.1.3
MMU Control
3.1.3.1
Invalidate (Flush) Operation
The entire instruction and data TLB can be invalidated at the same time with one
command or they can be invalidated separately. An individual entry in the data or
instruction TLB can also be invalidated. See
Table 21, “TLB Functions” on page 105
for
a listing of commands supported by the Intel XScale processor.
Globally invalidating a TLB will not affect locked TLB entries. However, the invalidate-
entry operations can invalidate individual locked entries. In this case, the locked
contents remain in the TLB, but will never “hit” on an address translation. Effectively,
creating a hole is in the TLB. This situation may be rectified by unlocking the TLB.
3.1.3.2
Enabling/Disabling
The MMU is enabled by setting bit 0 in coprocessor 15, register 1 (Control Register).
When the MMU is disabled, accesses to the instruction cache default to cacheable
accesses and all accesses to data memory are made non-cacheable.
A recommended code sequence for enabling the MMU is shown in
Table 8.
Valid MMU & Data/Mini-Data Cache Combinations
MMU
Data/mini-data Cache
Off
Off
On
Off
On
On