X-QSPI Application Note

1. Introduction to Basic Functions

  • The “X” in X-QSPI stands for eXecute-in-place, meaning that code can be executed directly from the NOR Flash connected to X-QSPI. In contrast, external QSPI can only be used for data storage and cannot store or execute code. To enable code execution, X-QSPI and external QSPI have functional differences and cannot be used interchangeably.

  • To accelerate code hit and execution efficiency, X-QSPI is designed with an instruction cache mechanism, all with sleep retention functionality. The cache sizes for different chips are as follows:

    • GR551x: 8 KB

    • GR5525: 8 KB

    • GR5526: 8 KB

    • GR533x: 8 KB

  • Several series of chips offer package models with 1 Mbyte of integrated NOR Flash, which can be used to store code and small amounts of data. When the 1 Mbyte model does not meet product design requirements, the external X-QSPI Flash version of each chip can be used. The external Flash capabilities are as follows:

    • GR551x: Supports up to 16 Mbytes of external X-QSPI Flash space, but only the lower 8 Mbytes support XIP mode. The upper 8 Mbytes require register addressing mode and are used only for data storage, not for code storage.

    • GR5525: Supports up to 16 Mbytes of external X-QSPI Flash space, all supporting XIP mode.

    • GR5526: No chip package supports external X-QSPI Flash.

    • GR533x: Supports up to 16 Mbytes of external X-QSPI Flash space, all supporting XIP mode.

  • The main frequency and maximum operating frequency of X-QSPI for different chips are as follows:

    • GR551x: 64 MHz / 64 MHz

    • GR5525: 96 MHz / 64 MHz

    • GR5526: 96 MHz / 64 MHz

    • GR533x: 64 MHz / 64 MHz

2. Application Notes

  • During program execution with X-QSPI, writing to Flash will disable the system’s global interrupts, which affects the timing logic of Bluetooth LE. Refer to the Application Note section “Handling Conflicts Between Bluetooth LE and Flash Code Execution” for program optimization in such scenarios.

  • The GR5515I0NDA uses external X-QSPI Flash. Since Flash from different manufacturers and models have varying functionalities and usage limitations, users can refer to the “GR5515I0NDA External Flash Selection Guide” to make appropriate selections based on the actual product situation. The guide provides instructions and electrical compatibility requirements for external Flash expansion and recommends a list of suggested selections, which can be downloaded from the official website. Other chip series can also use this document as a reference.

  • If users need to implement special Flash instructions, they should pay attention to the conversion between XIP and QSPI states. Refer to the example code in the SDK\components\libraries\hal_flash\hal_exflash_user_operation.c file to implement it themselves. Since code on Flash cannot be executed during Flash operations, ensure to add the SECTION_RAM_CODE macro before the operation functions to execute them in SRAM.