ADSP-BF535 Blackfin Processor Hardware Reference
6-63
Memory
exception is generated before the memory is modified. Optionally, the
User mode application may be granted read access for data structures that
are useful to the application. Even Supervisor mode functions can be
blocked from writing some memory pages that contain code that is not
expected to be modified. Because CPLB entries are MMRs that can be
written only while in Supervisor mode, user programs cannot gain access
to resources protected in this way.
If either the L1 Instruction Memory or the L1 Data Memory is configured
partially or entirely as cache, the corresponding CPLBs must be enabled.
When an instruction generates a memory request and the cache is enabled,
the processor first checks the ICPLBs to determine whether the address
requested is in a cacheable address range. If no valid ICPLB entry in an
MMR pair corresponds to the requested address, an MMU exception is
generated to obtain a valid ICPLB descriptor to determine whether the
memory is cacheable or not. As a result, if the L1 Instruction Memory is
enabled as cache, then any memory region that may contain instructions
must have a valid ICPLB descriptor defined for it. These descriptors must
either reside in MMRs at all times or be resident in a memory-based Page
Descriptor Table that is managed by the MMU exception handler.
Likewise, if either or both L1 data banks are configured as cache, all
potential data memory ranges must be supported by DCPLB descriptors.
Before caches are enabled, the MMU and its supporting data struc-
tures must be set up and enabled.
Examples of Protected Memory Regions
In
Figure 6-21
, a starting point is provided for basic CPLB allocation for
Instruction and Data CPLBs. Note that some ICPLBs and DCLBs have
common descriptors for the same address space. For example, on-chip L2
memory would typically be configured as cacheable with an instruction
and data CPLB. In such a case, external memory would take advantage of
the page replacement mechanism described in the section above.
Содержание ADSP-BF535 Blackfin
Страница 80: ...Development Tools 1 26 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 312: ...Working With Memory 6 86 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 332: ...System Interfaces 7 20 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 360: ...Dynamic Power Management Controller 8 28 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 446: ...Beginning and Ending an SPI Transfer 10 40 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 522: ...Timing Examples 11 76 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 562: ...IrDA Support 12 40 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 608: ...PCI I O Issues 13 46 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 672: ...References 14 64 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 810: ...SDRAM Controller SDC 18 86 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 811: ...ADSP BF535 Blackfin Processor Hardware Reference 18 87 External Bus Interface Unit...
Страница 812: ...SDRAM Controller SDC 18 88 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 860: ...DMA Bus Debug Registers 20 30 ADSP BF535 Blackfin Processor Hardware Reference...
Страница 908: ...SDRAM Controller External Bus Interface Unit B 36 ADSP BF535 Blackfin Processor Hardware Reference...