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| Home > Program Trace Macrocell Programmer’s Model > Instrumentation resources | |||
Instrumentation resources provide a simple, low-overhead method of controlling tracing from software, based on:
The provision of up to four PTM event resources, Instrumentation resource 1 to Instrumentation resource 4. For more information, see The Instrumentation resource event resources.
Instructions in the ARM and Thumb instruction sets that control these resources. These instructions can:
Set a specified Instrumentation resource, for the current and following cycles.
Clear a specified Instrumentation resource, for the current and following cycles.
Pulse a specified Instrumentation resource. This means the resource is set for the current cycle, cleared for the next cycle, and remains clear for following cycles. If the resource is already set then it remains set for the current cycle and is cleared from the next cycle.
For more information, see Instructions for controlling the Instrumentation resources.
Using these PTM event resources to define PTM events, as described in Event resources and PTM events.
For a PTM implementation, the number of Instrumentation resources is implementation defined:
a PTM implementation does not have to provide any Instrumentation resources
the maximum number of Instrumentation resources is four.
Bits [15:13] of the Configuration Code Extension Register specify the number of Instrumentation resources implemented, see Configuration Code Extension Register, ETMCCER.
In addition, if the PTM implements at least one Instrumentation resource, you can use the Instrumentation resource control bit, bit [24], of the Main Control Register to control the availability of Instrumentation resource programming. If this bit is set to 1, the Instrumentation resources can be programmed only when the processor is in a privileged mode. For more information see Main Control Register, ETMCR.
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