ARM Architecture Reference Manual ARMv7-A and ARMv7-R edition

C10.6 OS Save and Restore registers, v7 Debug only
Debug Registers Reference
Support for the OS Save and Restore mechanism registers depends on the Debug architecture version:
v6 Debug and v6.1 Debug
These registers are not defined.
v7 Debug If an implementation supports debug over power-down, then it must implement the OS Save
and Restore mechanism registers. On SinglePower systems, and on any other system that
does not support debug over power-down, it is IMPLEMENTATION DEFINED whether the OS
Save and Restore mechanism is implemented.
Any implementation that does not support the OS Save and Restore mechanism must
implement the DBGOSLSR as RAZ.
This section describes the registers that provide the OS Save and Restore mechanism in the following
subsections:
OS Lock Access Register (DBGOSLAR)
OS Lock Status Register (DBGOSLSR) on page C10-76
OS Save and Restore Register (DBGOSSRR) on page C10-77.
In addition, the Event Catch Register enables the generation of a debug event when the OS Lock is unlocked.
This register is described in Event Catch Register (DBGECR) on page C10-78.
C10.6.1 OS Lock Access Register (DBGOSLAR)
The OS Lock Access Register, DBGOSLAR, provides a lock for the debug registers. When the registers
have been locked any access to the registers returns a slave-generated error response. Writing the key value
to the DBGOSLAR has the side effect of resetting the internal counter for the OS Save or Restore operation.
You must use the DBGOSLSR to check the current status of the lock, see OS Lock Status Register
(DBGOSLSR) on page C10-76.
The DBGOSLAR is:
debug register 192, at offset 0x300
a write-only register
only defined in v7 Debug
when the Security Extensions are implemented, a Common register.
Note
In a v7 Debug implementation that does not implement the OS Save and Restore mechanism, register 192
ignores writes.
In v6 Debug and v6.1 Debug, register 192 is not defined.
ARM DDI 0406B Copyright © 1996-1998, 2000, 2004-2008 ARM Limited. All rights reserved. C10-75