RealView Platform Baseboard for Cortex-A8 User Guide: 4.3.5. Lock Register, SYS

4.3.5. Lock Register, SYS_LOCK

The SYS_LOCK register at 0x10000020 locks or unlocks access to all lockable registers.

Lockable registers cannot be modified while they are locked. This mechanism prevents the registers from being overwritten accidently. The registers are locked by default after a reset.

Figure 4.6 shows the register bit assignment.

Figure 4.6. SYS_LOCK register

The function of the register bits are shown in Table 4.9.

Table 4.9. SYS_LOCK register bit assignments

Bits	Access	Name	Reset	Description
[31:20]	Write ignored, read as zero	−	`0x000`	Undefined
[19:17]	Write ignored, read as zero	−	`b00`	Undefined
[16]	Read-only	LOCKED	`b1`	This bit indicates if the lockable registers are locked or unlocked: `b0` = unlocked `b1` = locked.
[15:0]	Read/Write	LOCKVAL	`0x0000`	Write the value `0xA05F` to unlock the lockable registers. Write any other value to this register to lock them.

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