2.14. Behavior when non-invasive debug is disabled

Some systems support the Security Extensions that enable non-invasive debug to be disabled. Sometimes a signal called NIDEN, Non Invasive Debug ENable, is used to disable or enable ETM functionality. Systems do not have to support the Security Extensions to implement this functionality.

When non-invasive debug is disabled, the ETM behaves as if the processor has entered a prohibited region. For more information, see Behavior while tracing is prohibited. The following additional restrictions apply:

As defined in the CoreSight Architecture Specification, the effect of the timing of disabling non-invasive debug is imprecise. Therefore, tracing might continue after non-invasive debug is disabled, and might take time to re-enable when non-invasive debug is re-enabled.

When non-invasive debug is disabled, the ETMAUTHSTATUS register represents this. For more information, see Authentication Status Register, ETMAUTHSTATUS, ETMv3.2 and later.

When non-invasive debug is disabled, the ETM programmers’ model behaves normally.

ARMv7 processors must implement the NIDEN functionality, and ETMs that are connected to ARMv7 processors must implement this functionality.

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