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

in Non-secure state and also in Secure User mode.
Invasive Debug Authentication
When Secure User halting debug is not supported, the processor can be configured only so that invasive
non-halting debug is permitted in Secure User mode when invasive debug is not permitted in Secure
privileged modes. Any debug event that would cause entry to Debug state is ignored, unless it is a BKPT
Instruction debug event. Therefore, the alternatives for when a debug event is permitted are:
in all processor modes, in both Secure and Non-secure security states
only in Non-secure state
in Non-secure state and also, if it will not cause entry to Debug state, in Secure User mode.
In v6.1 Debug and v7 Debug, invasive debug authentication can be controlled dynamically, meaning that
whether a debug event is permitted can change while the processor is running, or while the processor is in
Debug state. For more information, see Generation of debug events on page C3-40.
In v6 Debug, invasive debug authentication can be changed only while the processor is in reset.
In the recommended external debug interface, the signals that control the enabling and permitting of debug
events are DBGEN and SPIDEN. SPIDEN is only implemented on processors that implement Security
Extensions. See Authentication signals on page AppxA-3.
Part C of this manual assumes that the recommended external debug interface is implemented.
Note
DBGEN and SPIDEN also control non-invasive debug, see About non-invasive debug authentication
on page C7-2.
For more information about use of the authentication signals see Changing the authentication signals
on page AppxA-4.
If DBGEN is LOW, all invasive debug is disabled.
On processors that do not implement Security Extensions, if DBGEN is HIGH, invasive debug is enabled
and permitted in all modes, see Table C2-1:
Table C2-1 Invasive debug authentication, Security Extensions not implemented
DBGEN Modes in which invasive debug is permitted
LOW None. Invasive debug is disabled.
HIGH All modes.
On processors that implement the Security Extensions, if both DBGEN and SPIDEN are HIGH, invasive
debug is enabled and all debug events are permitted in all modes and in both Secure and Non-secure security
states.
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