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3.15.3 STM8 Memory Models

SDCC implements two memory models for the STM8: medium (default) and large. Modules compiled with different memory models should never be combined together. The library routines supplied with the compiler are compiled for all models.

In the medium model the address space is 16 bits for both objects and functions, allowing for a memory space of 64 KB. Since the STM8 typically has Flash starting at 0x8000, this means that only up to 32 KB of Flash can be used (most STM8 devices don't have more than 32 KB of Flash).

In the large memory model, the address space is 16 bits for objects and 24 bits for functions. Since the STM8 typically has flash starting at 0x8000, this means that up to 32 KB of flash can be used for constant data, while the whole Flash can be used for functions. Code generated for the large model is slightly bigger and slower and needs slightly more stack space than code generated for the medium model.