6.5.4. Normal TFO packets

A normal TFO packet comprises the following contiguous components:

A header byte

Broadcast first. The TFO header byte includes the 2-bit reason code that is labeled as RR in Table 6.6). For more information about TFO reason codes, see TFO reason codes.

Context ID

The number of Context ID bytes traced (0 to 4) is statically determined by ETMCR bits [15:14]. For more information on Context ID, see Context ID tracing.

Instruction address

The instruction address is always four bytes and is not compressed. Bit [0] specifies the Thumb bit.

TFO reason codes

The TFO reason codes are consistent with the branch reason codes used in ETMv1.0 and ETMv1.1. Table 6.7 shows the TFO reason codes.

Table 6.7. TFO reason codes

ValueDescription
b00Normal synchronization
b01Tracing has been enabled
b10Trace restarted after overflow
b11ARM processor has exited from debug state

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