8.5.4 Region Lock Register

The region x descriptor PRxLOCK register has two fields: a 16-bit KEY[15:0] field and 2-bit LOCK[1:0] field.

Writes to the register must be 32 bits (long word) and have the correct KEY value of 0xB737. Otherwise, the write is ignored. The LOCK field has three options:

• Region descriptor unlocked (LOCK[1:0] bits = ‘11’)
• Region descriptor locked, cannot be unlocked until after the next reset (LOCK[1:0] bits = ‘01’)
• Region descriptor locked (LOCK[1:0] bits = ‘00’)

If the descriptor is locked, the PRxCTRL, PRxST and PRxEND registers are read-only. The Reset value for the LOCK[1:0] field is region descriptor locked, so a PRxLOCK register write is required to unlock the descriptor. The PRxLOCK register is not used for OTP and IRT region descriptors, which cannot be modified.