1.1.2. The CoreSight debug environment

The PTM is designed for use with CoreSight, an extensible, system-wide debug and trace architecture from ARM.

A software debugger provides the user interface to the PTM. You can use this interface to configure the PTM facilities such as filtering and optional parts of the trace, such as timestamping. The same user interface is used to configure the other CoreSight components such as the Trace Port Interface Unit (TPIU), and to access the processor debug and performance monitor units. The debugger also interprets the trace information that has been output.

In addition, a CoreSight system can provide memory mapped access from the processor to its own debug and trace components.

The PTM outputs its trace stream to the AMBA 3 ATB interface. The CoreSight infrastructure provides the following options:

The debugger extracts the captured trace data from the TPA or ETB and decompresses it to provide full disassembly, with symbols, of the code that was executed. The PTM provides to the debugger the capability to link this data back to the original high-level source code, to provide a visualization of how the code was executed on the target system.

The PTM provides a mechanism for inserting a global timestamp in the trace stream that it generates. You can use this as an alternative or in addition to the cycle counting function. Trace tools can use timestamps to correlate trace from several trace sources. To use the timestamp function, the system integrator must provide a timestamp count to all trace sources that generate timestamps.

Figure 1.1 shows how the PTM fits into the CoreSight debug environment. See the CoreSight Architecture Specification for more information.

In Figure 1.1, the PTM and the Cross Trigger Interface (CTI), are part of a CoreSight system consisting of other processors with PTMs, and various other trace sources. You can program the CoreSight components using the Debug Access Port (DAP) through the CoreSight Debug APB bus. The system outputs trace over the ATB trace bus, and either exports it through the Trace Port Interface Unit (TPIU), or stores it in the Embedded Trace Buffer (ETB). Figure 1.1 shows the trace sources connecting to both a TPIU and the ETB.

Figure 1.1. Example CoreSight debug environment

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