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Should a slave respond with an error or OKAY response when the user addresses memory space in the slave that has no registers?

Applies to: AXI

Answer

It is implementation dependent how a slave should respond when a user accesses a location in the slave where there is no register present, but it is recommended that the behaviour that is chosen is documented in the slave manual.

Providing an error response to all illegal accesses has the advantage that it helps to quickly detect when an erroneous software access occurs and therefore can help to speed up the debug process.

However, there can be times when it is not recommended to provide an error response for every possible illegal access. An example of this would be where a master, which may be a DMA engine or possibly a debugger interrogating a slave, simply performs a burst access across a number of locations rather than reading individual locations. In such circumstances providing an error response could cause the operation to fail.

Article last edited on: 2008-09-09 15:47:44

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