Nios® V Processor Software Developer Handbook

ID 743810
Date 7/20/2023
Public

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6.8. Using Flash Devices

The HAL provides a generic device model for nonvolatile flash memory devices. Flash memories use special programming protocols to store data. The HAL API provides functions to write data to flash memory. For example, you can use these functions to implement a flash-based file subsystem.

The HAL API also provides functions to read flash, although it is generally not necessary. For most flash devices, programs can treat the flash memory space as simple memory when reading, and do not need to call special HAL API functions. If the flash device has a special protocol for reading data, you must use the HAL API to both read and write data.

This section describes the HAL API for the flash device model. The following two APIs provide two different levels of access to the flash:

  • Simple flash access—Functions that write buffers to flash and read them back at the block level. In writing, if the buffer is less than a full block, these functions erase preexisting flash data above and below the newly written data.
  • Fine-grained flash access—Functions that write buffers to flash and read them back at the buffer level. In writing, if the buffer is less than a full block, these functions preserve preexisting flash data above and below the newly written data. This functionality is generally required for managing a file subsystem.

The API functions for accessing flash devices are defined in sys/alt_flash.h.

The supportable flash IP for Nios® V processor is the Generic Serial Flash Interface Intel FPGA IP.