2.2.3. Trace sources

Sources generate trace data and provide master ports to the AMBA Trace Bus. Depending on the licensed CoreSight components, the following trace sources can be provided:

CoreSight Technology also enables you to add third party devices, for example a DSP trace component.

AHB Trace Macrocell (HTM)

The HTM makes bus information visible that you can not infer from core trace using an ETM:

  • An understanding of multi-layer bus utilization.

  • Software debug. For example, visibility of access to memory areas and data accesses.

  • Bus event detection for trace trigger or filters, and for bus profiling.

Figure 2.3 shows the HTM connected to an AHB bus. For more information on HTM see the AMBA Trace Macrocell Technical Reference Manual.

Figure 2.3. HTM connected to a multi-layer AHB system

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Instrumentation Trace Macrocell and System Trace Macrocell

The Instrumentation Trace Macrocell (ITM) and System Trace Macrocell (STM) are application-driven trace sources that generate trace based on software written to the program interface. The ITM presents 32 APB registers, and the STM provides a set of 64K AXI registers that, on a write transaction, generate corresponding trace that indicates the register and value written.

Embedded Trace Macrocells (ETMs) and Program Trace Macrocells (PTMs)

The ETMs provide processor-driven trace through an ATB-compliant trace port. You can configure the ETM through the CoreSight APB programming interface. ETM9CS and ETM11CS both provide an asynchronous ATB master port that transfers trace data onto the CoreSight infrastructure.

ETM9CS implements the ETMv3.2 protocol. ETM11CS implements the ETMv3.2 protocol with TrustZone™ and Thumb®-2 trace support.

ETM for Cortex-A8 and ETM for Cortex-R4 implement the ETMv3.3 protocol. However, the ETM for A8 is instruction and data address trace only.

ETM for Cortex-M3 implements the ETMv3.4 protocol. It only implements instruction trace.

PTM for Cortex-A9 implements the PTMv1 protocol to provide instruction flow trace.

For more information, see the following manuals:

  • appropriate CoreSight ETM Technical Reference Manual

  • Embedded Trace Macrocell Architecture Specification

  • CoreSight PTM-A9 Technical Reference Manual

  • Program Flow Trace Macrocell Architecture Specification.

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