# Optional Features for Flash

[中文]

Some features are not supported on all ESP chips and flash chips. You can check the list below for more information:

- Auto Suspend & Resume

- Flash Unique ID

- High Performance Mode of QSPI Flash Chips

- 32-bit Address Support of QSPI Flash Chips

- OPI Flash Support

Note

When Flash optional features listed in this page are used, aside from the capability of ESP chips and ESP-IDF version you are using, you will also need to make sure these features are supported by flash chips used:

- If you are using an official Espressif modules/SiP, please make sure that they support the above features by referring to the datasheet. Otherwise, please contact Espressif's business team to know if we can supply such products for you.

- If you are making your own modules with your own bought flash chips and need features listed above, please contact your vendor to see if they support those features, and make sure that the chips can be supplied continuously.

Attention

This document only shows that ESP-IDF code has supported the features of those flash chips. It is not a list of stable flash chips certified by Espressif. If you build your own hardware with your own brought flash chips (even with features listed in this page), you need to validate the reliability of flash chips yourself.

## Auto Suspend & Resume

This feature is only supported on ESP32-S3, ESP32-C2, ESP32-C3, ESP32-C6, and ESP32-H2 for now.

The support for ESP32-P4 may be added in the future.

List of flash chips that support this feature:

1. XM25QxxC series

2. GD25QxxE series

3. FM25Q32

Attention

There are multiple limitations about the auto-suspend feature, please do read Flash Auto Suspend Feature for more information before you enable this feature.

## Flash Unique ID

This feature is supported on all Espressif chips.

Unique ID is not flash id, which means flash has 64-bit unique ID for each device. The instruction to read the unique ID (4Bh) accesses a factory-set read-only 64-bit number that is unique to each flash device. This ID number helps you to recognize each device. Not all flash vendors support this feature. If you try to read the unique ID on a chip which does not have this feature, the behavior is not determined.

List of flash chips that support this feature:

1. ISSI

2. GD

3. TH

4. FM

5. Winbond

6. XMC

7. BOYA

## High Performance Mode of QSPI Flash Chips

This feature is only supported on ESP32-S3 for now.

The support for ESP32-S2, ESP32-C3, ESP32-C6, ESP32-H2, and ESP32-P4 may be added in the future.

Note

This section is provided for QSPI flash chips. Octal flash used on ESP-chips supports High Performance mode by default so far, please refer to OPI Flash Support for the list of supported octal flash chips.

High Performance mode (HPM) means that the SPI1 and flash chip works under high frequency. Usually, when the operating frequency of the flash is greater than 80 MHz, it is considered that the flash works under HPM.

As far as we acknowledged, there are more than three strategies for HPM in typical SPI flash parts. For some flash chips, HPM is controlled by dummy cycle (DC) bit in the registers, while for other chips, it can be controlled by other bits (like HPM bit) in the register, or some special command. The difference in strategies requires the driver to explicitly add support for each chip.

Attention

It is hard to create several strategies to cover all situations, so all flash chips using HPM need to be supported explicitly. Therefore, if you try to use a flash not listed in Quad Flash HPM support list, it might cause some error. So, when you try to use the flash chip beyond supported list, please test properly.

Moreover, when the DC adjustment strategy is adopted by the flash chip, the flash remains in a state in which DC is different from the default value after a software reset. The sub mode of HPM that adjusts the DC to run at higher frequency in the application is called HPM-DC. HPM-DC feature needs a feature DC Aware to be enabled in the bootloader. Otherwise different DC value will forbid the 2nd bootloader from being boot up after reset.

To enable High Performance mode:

1. De-select CONFIG_ESPTOOLPY_OCT_FLASH and CONFIG_ESPTOOLPY_FLASH_MODE_AUTO_DETECT. HPM is not used for Octal flash, enabling related options may bypass HPM functions.

2. Enable `CONFIG_SPI_FLASH_HPM_ENA` option.

3. Switch flash frequency to HPM ones. For example, `CONFIG_ESPTOOLPY_FLASHFREQ_120M`.

4. Make sure the config option for HPM-DC feature (under `CONFIG_SPI_FLASH_HPM_DC` choices) is selected correctly according to whether the bootloader supports DC Aware.

   > - If bootloader supports DC Aware, select `CONFIG_SPI_FLASH_HPM_DC_AUTO`. This allows the usage of flash chips that adopted DC adjustment strategy.

   > - If bootloader doesn't support DC Aware, select `CONFIG_SPI_FLASH_HPM_DC_DISABLE`. It avoids consequences caused by running HPM-DC with non-DC-aware bootloaders. But please avoid using flash chips that adopts DC adjustment strategy if `CONFIG_SPI_FLASH_HPM_DC_DISABLE` is selected. See list of flash models that adpot DC strategy below.

Check whether the bootloader supports DC Aware in the following way:

- If you are starting a new project, it's suggested to enable DC Aware by selecting CONFIG_BOOTLOADER_FLASH_DC_AWARE option in the bootloader menu. Please note that, you won't be able to modify this option via OTA, because the support is in the bootloader.

- If you are working on an existing project and want to update HPM-DC config option in the app via OTA, check the sdkconfig file used to build your bootloader (upgrading ESP-IDF version may make this file different from the one used by bootloader to build):

  > - For latest version (v4.4.7+, v5.0.7+, v5.1.4+, v5.2 and above), if CONFIG_BOOTLOADER_FLASH_DC_AWARE is selected, the bootloader supports DC Aware.

  > - For other versions (v4.4.4-v4.4.6, v5.0-v5.0.6, and v5.1-v5.1.3), if `CONFIG_ESPTOOLPY_FLASHFREQ_120M` is selected, the bootloader supports DC Aware. In this case, enable CONFIG_BOOTLOADER_FLASH_DC_AWARE to confirm this (though it will not affect bootloader in devices in the field).

  > - For versions below v4.4.4, the bootloader doesn't support DC Aware.

### Quad Flash HPM support list

Flash chips that don't need HPM-DC:

1. GD25Q64C (ID: 0xC84017)

2. GD25Q32C (ID: 0xC84016)

3. ZB25VQ32B (ID: 0x5E4016)

4. GD25LQ255E (ID: 0xC86019)

Following flash chips also have HPM feature, but requires the bootloader to support DC Aware:

1. GD25Q64E (ID: 0xC84017)

2. GD25Q128E (ID: 0xC84018)

3. XM25QH64C (ID: 0x204017)

4. XM25QH128C (ID: 0x204018)

## 32-bit Address Support of QSPI Flash Chips

This feature is supported on all Espressif chips (see restrictions to application below).

Note

This section is provided for QSPI flash chips. The 32-bit address support of Octal flash chips are considered as part of the Octal flash support. Please refer to OPI Flash Support for the list of supported octal flash chips.

Most NOR flash chips used by Espressif chips use 24-bits address, which can cover 16 MB memory. However, for larger memory (usually equal to or larger than 32 MB), flash uses a 32-bits address to address memory region higher than 16 MB. Unfortunately, 32-bits address chips have vendor-specific commands, so we need to support the chips one by one.

List of Flash chips that support this feature:

1. W25Q256

2. GD25Q256

### Restrictions

By default, space over 16 MB on flash mentioned above can be used for `data saving`, like file system.

Furthermore, to map data/instructions to 32-bit physical address space (so as to be accessed by the CPU), please enable the config `IDF_EXPERIMENTAL_FEATURES` and `BOOTLOADER_CACHE_32BIT_ADDR_QUAD_FLASH`.

Please note that, this option is experimental, which means that it can not be used on all flash chips stably. For more information, please contact Espressif's business team.

## OPI Flash Support

This feature is only supported on ESP32-S3 for now.

OPI flash means that the flash chip supports octal peripheral interface, which has octal I/O pins. Different octal flash has different configurations and different commands. Hence, it is necessary to carefully check the support list.

Note

To know how to configure menuconfig for a board with different flash and PSRAM, please refer to How to Configure Flash and PSRAM.

List of flash chips that support this feature:

1. MX25UM25645G

2. MX25UM12345G

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