Nios® V Embedded Processor Design Handbook

ID 726952
Date 7/16/2025
Public

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Ixiasoft

Document Table of Contents

2.3.1.4.2. Using Address Span Extender IP with Nios® V Processor

The 32-bit Nios® V processor can address up to 4 GB of an address span. If the EMIF contains more than 4GB of memory, it exceeds the maximum supported address span, rendering the Platform Designer system as erroneous. An Address Span Extender IP is required to resolve this issue by dividing a single EMIF address space into multiple smaller windows.
Altera recommends that you consider the following parameters.
Table 21.  Address Span Extender Parameters
Parameter Recommended Settings
Datapath Width Select 32-bits, which corelates to the 32-bit processor.
Expanded Master Byte Address Width Depends on the EMIF memory size.
Slave Word Address Width Select 2 GB or less. Remaining address span of Nios® V processor is reserved for other embedded soft IPs.
Burstcount Width Start with 1 and gradually increase this value to improve performance.
Number of sub-windows Select 1 sub-window if you are connecting EMIF to the Nios® V processor as instruction and data memory, or both. Switching between multiple sub-windows while Nios® V processor is executing from EMIF is hazardous.
Enable Slave Control Port Disable the slave control port if you are connecting EMIF to the Nios® V processor as instruction and/or data memory. Same concerns as Number of sub-windows.
Maximum Pending Reads Start with 1 and gradually increase this value to improve performance.
Figure 14. Connecting Instruction and Data Manager to Address Span Extender
Figure 15. Address Mapping
Notice that the Address Span Extender can access the whole 8GB memory space of the EMIF. However, via the Address Span Extender, the Nios® V processor can access only the first 1GB memory space of the EMIF.
Figure 16. Simplified Block Diagram