ARM Cortex-A15 MPCore Processor Technical Reference Manual

Program Trace Macrocell12.3 PTM functional descriptionThis section describes the PTM in:• Processor interface.• Trace generation.• Filtering and triggering resources on page 12-5.• FIFO on page 12-5.• Trace out on page 12-5.Figure 12-1 shows the main functional blocks of the PTM.CLKPTMProcessorinterfaceProcessorinterface blockTrace generationDebug APBFiltering and triggering resourcesFIFOATCLKENTrace outATBFigure 12-1 PTM functional blocks12.3.1 Processor interfaceThis block monitors the behavior of the processor and generates waypoint information.12.3.2 Trace generationThe PFT architecture assumes that the trace tools can access a copy of the code being traced.For this reason, the PTM generates trace only at certain points in program execution, calledwaypoints. This reduces the amount of trace data generated by the PTM compared to the ETMprotocol. Waypoints are changes in the program flow or events, such as an exception. The tracetools use waypoints to follow the flow of program execution. For full reconstruction of theprogram flow, the PTM traces:• Indirect branches, with target address and condition code.• Direct branches with only the condition code.• Instruction Synchronization Barrier.• Exceptions, with an indication of where the exception occurred.• Exceptions, with an indication of where the exception returned.• Changes in processor instruction set state.• Changes in processor security state.• Changes in Context ID• Changes in VMID.• Entry to and return from Debug state when Halting Debug-mode is enabled.ARM DDI 0438I Copyright © 2011-2013 ARM. All rights reserved. 12-4ID062913Non-Confidential