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12.5.8. Lock Access Register

The Lock Access Register is a write-only register that controls writes to the debug registers. The purpose of the Lock Access Register is to reduce the risk of accidental corruption to the contents of the debug registers. It does not prevent all accidental or malicious damage. Because the state of the Lock Access Register is in the debug power domain, it is not lost when the core powers down.

Figure 12.25 shows the bit arrangement of the Lock Access Register.

Figure 12.25. Lock Access Register format

Figure 12.25. Lock Access Register format

Table 12.40 shows how the bit values correspond with the Lock Access Register functions.

Table 12.40. Lock Access Register bit functions


Lock access controlLock access control. To unlock the debug registers, write a 0xC5ACCE55 key to this register. To lock the debug registers, write any other value. Accesses to locked debug registers are ignored.


You can only access the Lock Access Register when the PADDR31 input is LOW. Writes are ignored when PADDR31 is HIGH.