7.2. Packet types

All trace information is output in packets over a single set of trace pins, TRACEDATA. See Trace port interface for information on TRACEDATA. Each packet comprises:

The headers are defined in the following paragraphs and are described in more detail later in this chapter.

The header encodings are listed in Table 7.1.

Table 7.1. Header encodings

Header descriptionValuePayload (max bytes)CategoryRemarks
Branch addressbCxxxxxx1Additional address bytes (5)Instruction

No header. C = another byte follows.

See Branch Packets.

A-syncb00000000None but repeatedSync.

Alignment synchronization.

See A-sync, alignment synchronization.

Cycle count b00000100Cycle count (5)Instruction

1 to (232-1) x W (see P-headers).

See Cycle count packet.

I-syncb00001000[a] (14)Sync.

Instruction flow synchronization.

See I-sync instruction synchronization.

Triggerb00001100NoneTrace portSee Trigger.
Out-of-order datab0TT0SS00Data value (4)Data

TT = tag (1-3), SS = data value size.

See Out-of-order data.

Store failedb01010000NoneDataFor use with the STREX instruction.
I-sync with cycle countb01110000[a] (19)Sync.

See I-sync instruction synchronization.

Out-of-order placeholderb01A1TT00Address (5)Data

TT = tag (1-3), A = Address follows where address tracing is enabled.

See Out-of-order placeholder.

VMIDb00111100Virtual Machine ID (1)Instruction

See VMID packets, ETMv3.5, ETMv3.5.

Normal datab00A0SS10

Address (5)

Data value (4)


A = address expected, SS = data value size.

See Normal data packet.

Timestampb01000x101-7 bytesSync.

See Timestamp packet, ETMv3.5.

Data suppressedb01100010NoneData

See Data suppressed packet.

Ignoreb01100110NoneTrace portSee Ignore.
Value not tracedb011A1010Address (5)Data

A = address follows.

See Value not traced packet.

Context IDb01101110Context ID (4)Instruction

See Context ID packets.

Exception exitb01110110NoneInstructionSee Tracing return from an exception.
Exception entryb01111110NoneInstructionAutomatic stack push on exception entry and pop on exception exit.
P-headerb1xxxxxx0NoneInstructionSee P-headers.

[a] For more information, see the section referred to in the Remarks column.

Headers are described in the following sections:

Some bits in the payload of certain packets are defined as Reserved. These bits are always zero in current versions of the architecture, but might indicate additional information in future versions. These bits can be ignored.

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