Relationship between RAM actually used by SoftDevice and APP_RAM_START

[loquat]

Hello. I have one question.

When configuring RAM with the nRF5 SDK + SoftDevice, if I get the following error:
APP_RAM_START=0x20006000
-------------------------------------------------------------------------------------
uint32_t ram_start = 0;
nrf_sdh_ble_default_cfg_set(BLE_CONN_CFG_TAG, &ram_start);
/* ram_start=0x20006000 */
nrf_sdh_ble_enable(&ram_start);
/* ram_start=0x20004000 */
-------------------------------------------------------------------------------------
Is the RAM from 0x20004000 to 0x20005FFF used by the SoftDevice? Or can it be freely used by the app?

[Turbo J]

Could in theory be used by the app.

In practise you would need to change linker settings - that is where the first ram_start is set from.

[Simonr]

This depends on what SoftDevice variant and version you're using. The amount of data the SoftDevice uses is stated in the specification. See S112 for reference here: https://docs.nordicsemi.com/bundle/sds_s112/page/SDS/s1xx/mem_usage/mem_resource_reqs.html#d92e151 

And as Turbo J  says, you will need to change the linker settings to make this happen on your side.

Best regards,

Simon

[loquat]

Sorry. I wrote "error," but that's incorrect.
What I want to know:
Does the SoftDevice not access RAM above the address returned by nrf_sdh_ble_enable (ram_start)?