Cortex-A8 R2P2.pdf - ARM Information Center

Debug12.5.8 Lock Access RegisterThe Lock Access Register is a write-only register that controls writes to the debugregisters. The purpose of the Lock Access Register is to reduce the risk of accidentalcorruption to the contents of the debug registers. It does not prevent all accidental ormalicious damage. Because the state of the Lock Access Register is in the debug powerdomain, it is not lost when the core powers down.Figure 12-25 shows the bit arrangement of the Lock Access Register.31 0Lock access controlBits Field FunctionFigure 12-25 Lock Access Register formatTable 12-40 shows how the bit values correspond with the Lock Access Registerfunctions.Table 12-40 Lock Access Register bit functions[31:0] Lock access control Lock access control. To unlock the debug registers, write a 0xC5ACCE55 key to thisregister. To lock the debug registers, write any other value. Accesses to locked debugregisters are ignored.NoteYou can only access the Lock Access Register when the PADDR31 input is LOW.Writes are ignored when PADDR31 is HIGH.12.5.9 Lock Status RegisterThe Lock Status Register is a read-only register that returns the current lock status ofthe debug registers.Figure 12-26 on page 12-64 shows the bit arrangement of the Lock Status Register.ARM DDI 0344E Copyright © 2006-2008 ARM Limited. All rights reserved. 12-63