| Copyright © 1999-2002, 2004-2009, 2011 ARM Limited. All rights reserved. | ARM IHI 0014Q |
| Non-Confidential | ID101211 |
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The ETM compresses the data trace by reducing the number of bits that are output for the address of the data transfer. The same technique is used as for branch addresses, where a copy of the last data access address is kept and only the low order bits that have changed are output for the next address.
This is particularly effective, for example, if you are viewing data in one small address range, because all the traced data accesses have the same high order address bits.
When the address of a data access is output it is compressed only if both of the following conditions are satisfied:
A full 32-bit data address has been
output in the synchronization period that ends with the current
cycle. The synchronization period is set in the Synchronization
Frequency Register, register 0x078, if present,
and otherwise is 1024 cycles.
There has been no interruption in tracing.
Otherwise no compression takes place, and the full 32-bit address is used to ensure that the captured trace information contains a reference point for the other compressed address packets.
| Copyright © 1999-2002, 2004-2009, 2011 ARM Limited. All rights reserved. | ARM IHI 0014Q |
| Non-Confidential | ID101211 |
| PDF version | |
| Home > ETMv2 Signal Protocol > Data tracing in ETMv2 > Address compression performed by the ETM |