hesela.devExecute-in-place
Execution of program instructions from their non-volatile storage location without first copying the executable code into a separate RAM image.
The system must provide an instruction-fetch path to the stored code. With serial flash, a controller can translate memory-mapped reads into flash transactions after the interface and read mode are configured. A chip's NOR label alone does not establish a working execute-in-place system. [1]
Execute-in-place does not eliminate RAM: caches, writable data, stacks and other runtime state can still use it. For a memory-mapped read-only filesystem, directly executed segments may require uncompressed, aligned storage while writable segments are copied to RAM. This differs from mapping a file backed by an SSD and fetching its pages into memory. [2]
Some flash documentation also calls a command-saving continuous-read mode XIP. That device feature can reduce read-command overhead, but it is not the complete system mechanism for executing stored instructions. [1]
Relations
- related
- nor-flash, nand-flash, byte-addressable-storage, memory-mapped-file, page-cache
Advantages
- Code can remain in non-volatile storage when RAM capacity is constrained. [2]
Limitations
- An update must account for program/erase activity that can block instruction reads from the same flash device. [3]
Citations
- STMicroelectronics. AN4760, Quad-SPI interface for STM32 MCUs and MPUs, revision 5, sections 3.3.3, 3.4.1 and 6.2: execution and continuous read.
- Linux kernel documentation. Cramfs: Memory Mapped cramfs image. Direct execution of aligned, uncompressed read-only segments and RAM for writable data.
- Infineon. Implementation of Program/Erase Suspend and Resume Operations in Serial NOR Flash. Busy-array access and suspend restrictions.
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Hesela team. Execute-in-place. Hesela. 2026-10-18. https://hesela.dev/terms/execute-in-place/