7.3.6. Context ID packets

When the Context ID changes, a Context ID packet is output to give the new value. It comprises the following components:

Figure 7.30 shows a Context ID packet.

Figure 7.30. Context ID packet

To view this graphic, your browser must support the SVG format. Either install a browser with native support, or install an appropriate plugin such as Adobe SVG Viewer.


The number of bytes output depends on the ContextIDSize bits, bits [15:14] of the ETMCR, register 0x000, see Main Control Register, ETMCR. If Context ID tracing is disabled because these bits are set to b00, Context ID packets are never generated.

If the Context ID is changed by a data transfer that would normally have been traced, and a Context ID packet is output, it is implementation specific whether the Context ID packet is generated instead of or in addition to the normal trace. As a result, when Context ID tracing is enabled, data trace might be missing for an instruction that changes the Context ID.

The Context ID packet is output:

Copyright © 1999-2002, 2004-2009, 2011 ARM Limited. All rights reserved.ARM IHI 0014Q
Non-ConfidentialID101211