1.1.4. Connections to a PTM

Figure 1.2 shows the main connections to a PTM.

Figure 1.2. Main connections to a PTM

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The PTM interfaces are:

Processor interface

This connects the PTM to the processor it is tracing, and carries all the information that is to be traced.

Programming interface

Use this interface to program the PTM registers, to configure and enable tracing and triggering. Typically, this interface is driven by a CoreSight DAP, that conforms to the ARM Debug Interface v5 Architecture Specification. The off-chip debugging tool drives the DAP through a JTAG or similar interface.

You can also drive the programming interface through a coprocessor interface or a memory-mapped interface. You can do this from the processor, or from on-chip bus fabric. This means software running on the system can configure and control tracing.

Trace output interface

The PTM uses this interface to output its trace data, for export to an off-chip Trace Port Analyzer or capture in an on-chip buffer. Typically, this interface is based on the AMBA Trace Bus (ATB) standard, for connection to a CoreSight trace capture device.

On-chip connections

These consist of additional implementation defined interfaces supported by a PTM. Typically, these include:

  • external inputs, for connections from a cross-triggering network

  • extended external inputs, typically used for connections from a performance monitor unit on the processor

  • external outputs, for connections to a cross-triggering network

  • a trigger output, to signal trigger events to trace capture devices

  • permitted debug control signals, for example a signal that disables noninvasive debug

  • timestamps, for use in correlating multiple trace streams.

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