9.6.3. Special modes of operation

The Formatter supports two distinct modes of operation as specified by bits [1:0] in the Formatter and Flush Control Register:

Bypass

In this mode, no formatting information is inserted into the trace stream and a raw reproduction of the incoming trace stream is stored. If any bytes remain in the formatter when tracing is stopped, because of non 32-bit ATDATAS, then the word stored to RAM is appended with a single logic 1 bit and filled in with zeros. A second word, 0x00000000 is then stored. If no bytes remain in the formatter, when capture is stopped, four additional words are stored, 0x00000001 then three words of 0x00000000.

When data is later decompressed it is then possible to determine that a post-amble is present by back tracking the trailing zero data at then end of the trace stream until the last single bit at logic 1 is detected. All data preceding this first logic 1 is then treated as decompressible data. When all data has been stored in the RAM, FtStopped in the Formatter and Flush Status Register is set HIGH.

Note

This mode assumes that the source ID is not changing.

Normal

Normal mode has the option of embedding triggers into the data packets.

Formatting information is added to indicate the change of source ID along with the associated wrapping additions, as described in TPIU formatter and FIFO. If any data remains in the formatter when tracing is stopped then the formatter is filled with NULL packets (ID = 0x00) to ensure all data is stored in RAM. When all remaining data has been stored in the RAM, FtStopped in the Formatter and Flush Status Register is set HIGH.

Continuous

Continuous mode in the ETB corresponds to normal mode with the embedding of triggers. Unlike continuous mode in the TPIU, no formatter synchronization packets are added because alignment of data to the RAM locations is assumed.

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