8.12.1. Operational description

Figure 8.20 shows the arrangement of four words and the positioning of the bits that are removed from some of the data packets.

When a trace source is changed the appropriate flag bit, F, is set (1 = ID, 0 = Data on the following byte). The second byte is always data and the corresponding bit at the end of the sequence (bits A-J) indicates if this second byte corresponds to the new ID (F bit clear) or the previous ID (F bit set).

If the trace source has not changed in eight formatter frames, an ID change is indicated, even though the new ID is the current ID value. This is done to ensure the external TCD log has a record in its buffer of the existing trace source.

Figure 8.20. Construction of formatter data packets

See the CoreSight Architecture Specification for more information on the formatter protocol.

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