nrf5 SDK ram noinit example

[William.wei]

hi support team,

customer is asking about 832 keil noinit setting, i did one in KEIL IDE， and find out that when i using nrfjprog --reset  or watchdog reset or download image reset, ram is not initialized, 

however when i reset device by pinreset with button reset in DK board, the ram is changed.

uint32_t print_data  __attribute__((at(0x2000FFF0)));

print_data++;
NRF_LOG_INFO("program restart SPI example started%8x",print_data);

i could not understand why reset will cause this difference?

is it possible to do such function(keep ram not changed) with noinit?

Regards,

William.

[Vidar Berg]

Hi William,

RAM retention through a pinreset is not guaranteed.  Please refer to the Reset behavior section of the product specification for more details.

Best regards,

Vidar

[William.wei]

Thanks Vidar,

may i ask what's the purpose of noinit, or how to use noinit?

as my understanding if we can't keep the ram value, it is useless.

Regards,

William.

[Vidar Berg]

The "noinit" section will not be initialized/overwritten by the startup code, so it can be used to hold data you want to retain across reboots. However, please note that RAM may not be retained for all reset sources, as indicated in the reset table I mentioned in my previous reply.