The AHB5 TrustZone memory protection controller provides a
configuration lockdown feature that prevents malicious software
from changing the security configuration. Writing
the security lockdown bit, CTRL, enables the configuration lockdown
Once the configuration lockdown feature is enabled:
It can only be disabled by a component reset which resets CTRL to 0x0.
The following registers are read-only:
ARM recommends that you write
0x1 to the
LUT autoincrement bit, CTRL before enabling the configuration
lockdown feature. When the feature is enabled only LUT reading is
available which is simpler when BLK_IDX increments automatically
during the read sequence.