nrf_hw_models/src/nrfx/hal/README.md

nRFx HAL

The HAL source files provided with these models implement some modifications to the real nRFx HAL needed due to the HW models peculiarities. Its main purpose is to allow unmodified embedded code to run directly using this repository HW models.

There is two main differences in this HAL compared to the real one:

• The peripherals base addresses point to the HW models register IF instead of to hardcoded HW addresses.
  For example NRF_PPI_BASE is defined as (&NRF_PPI_regs), where NRF_PPI_regs is the HW models structure containing the PPI model registers

• When a HW register with sideeffects is written, the appropriate HW model function is called to trigger that sideeffect.
  A sideeffect should be understood as some activity beyond the modification of the register itself. For example, in real HW, writting a 1 to NRF_RNG->TASKS_START will start the random number generation. When using the HW models, doing this write in itself would only change that memory location content. To trigger the actual sideeffect the function nrf_rng_regw_sideeffects_TASK_START() needs to be called. This replacement HAL functions take care of that.

The original implementation of the HAL APIs from the real nrfx is included in nrf_hal_originals.c. All these functions are labelled as weak, so they can be replaced as needed with content of src/nrfx/hal/. This removes the need for duplicating code.

Note that this replacement HAL only provides the necessary replacements for the subset of the nRFx API corresponding to the peripherals included in these models. Note also that for these, not necessarily all nRFx functions which could need replacing are included. Though those used by Zephyr should be included. It is certainly possible to expand it to cover the whole API.