| Copyright © 2001-2002 ARM Limited. All rights reserved. | ARM DDI 0242B |
| Non-Confidential | |
 PDF version | |
| Home > Programmer’s Model > Software access to the ETB using the AHB interface > Restrictions on use of the AHB interface |
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| Home > Programmer’s Model > Software access to the ETB using the AHB interface > Restrictions on use of the AHB interface | |||
The AHB interface can be used for two purposes:
to read trace data captured by the ETB from software
as system memory when tracing is not required.
When using the AHB interface to read trace data, the following are not permitted:
byte or halfword accesses
unaligned accesses
multi-word accesses (such as LDM or STM).
Only aligned, single word accesses are permitted.
Use of the AHB interface as system memory requires careful system design to ensure that the memory is not required for system use when tracing is required. If you wish to use the AHB interface for this purpose, you must ensure the following:
the memory supports byte writes (see the Embedded Trace Buffer Implementation Guide)
if connected to a 64 bit AHB bus, 64 bit operations are supported see Connecting the ETB in a 64-bit AHB system).
This is to ensure that all ARM load/store instructions are supported.
| Copyright © 2001-2002 ARM Limited. All rights reserved. | ARM DDI 0242B |
| Non-Confidential | |
| PDF version | |
| Home > Programmer’s Model > Software access to the ETB using the AHB interface > Restrictions on use of the AHB interface |