Embedded Design Handbook

ID 683689
Date 8/28/2023
Public
Document Table of Contents

5.2.4.4. Nios® II Processor Application Executes In-Place from Configuration QSPI Flash (Other FPGA devices)

The execute-in-place option is suitable for Nios® II processor applications which require limited on-chip memory usage.

The alt_load() function operates as a mini boot copier that initializes and copies the writable memory sections only to OCRAM or external RAM. The code section (.text), which is a read-only section, remains in the QSPI flash memory region. Retaining the read-only section in QSPI minimizes RAM usage but may limit the code execution performance.

The Nios® II processor application is programmed into the configuration QSPI flash. The Nios® II processor reset vector points to the configuration QSPI flash to allow code execution after the system resets. If you are debugging the application using the source-level debugger, you must use a hardware breakpoint because the configuration QSPI cannot support random memory access.