RE: Disengaging APPROTECT

Richard Yoo — Tue, 27 Oct 2020 13:37:19 GMT

That explains what we're observing. Thank you!

RE: Disengaging APPROTECT

Vidar Berg — Tue, 27 Oct 2020 07:34:17 GMT

Hi,

Unfortunately, on the 52840, the only way to disable APPROTECT is through a full chip erase. UICR is placed in FLASH memory, and on the nRF52832 you could always erase it with NVMC->ERASEUICR and thus allow you to disable readback protection from the program code. However, on the nrf52840, this operation becomes unavailable once read-back protection is enabled.

Excerpt from the NVMC chapter of the 52840 PS:

Access port protection behavior

When access port protection is enabled, parts of the NVMC functionality will be blocked in order to prevent intentional or unintentional erase of UICR.

Table 1. NVMC Protection
	CTRL-AP ERASEALL	NVMC ERASEPAGE	NVMC ERASEPAGE PARTIAL	NVMC ERASEALL	NVMC ERASEUICR
APPROTECT
Disabled	Allowed	Allowed	Allowed	Allowed	Allowed
Enabled	Allowed	Allowed	Allowed	Allowed	Blocked

Best regards,

Vidar