If the application’s memory requirements are small enough to fit entirely on chip, it is
possible to use tightly-coupled memory exclusively for code and data. Larger
applications must selectively choose what to include in tightly-coupled memory to
maximize the cost-performance trade-off.
Related Information
Using Tightly Coupled Memory with the Nios II Processor Tutorial
For additional tightly-coupled memory guidelines.
2.6.4. Address Map
The address map for memories and peripherals in a Nios II processor system is design
dependent. You specify the address map in Platform Designer.
There are three addresses that are part of the processor and deserve special mention:
•
Reset address
•
Exception address
•
Break handler address
Programmers access memories and peripherals by using macros and drivers.
Therefore, the flexible address map does not affect application developers.
2.6.5. Memory Management Unit
The optional Nios II MMU provides the following features and functionality:
•
Virtual to physical address mapping
•
Memory protection
•
32-bit virtual and physical addresses, mapping a 4-GB virtual address space into
as much as 4 GB of physical memory
•
4-KB page and frame size
•
Low 512 MB of physical address space available for direct access
•
Hardware translation lookaside buffers (TLBs), accelerating address translation
— Separate TLBs for instruction and data accesses
— Read, write, and execute permissions controlled per page
— Default caching behavior controlled per page
— TLBs acting as n-way set-associative caches for software page tables
— TLB sizes and associativities configurable in the Nios II Processor parameter
editor
•
Format of page tables (or equivalent data structures) determined by system
software
•
Replacement policy for TLB entries determined by system software
•
Write policy for TLB entries determined by system software
For more information about the MMU implementation, refer to the Programming Model
chapter of the Nios II Processor Reference Handbook.
2. Processor Architecture
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