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Complex register description

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I would like to describe a complex register. each register is spaced of 0x10

The register is of 4 bytes width and is seen at different address for different operations. ie :

register address + 0x0 -> replace whole register

register address + 0x4 -> set bits where set

register address + 0x8 -> reset bits where set

register address + 0xC -> toggle bits where set


Initially I was to use 3 alternate registers per register, but addressOffset is not element of alternate register. Only access may be different. So I have to add VendorExtension for addressOffset.

Another way could be to use the dim element to repeat the register 3 times. Also here, the register is the same in its behaviour.

There could be also bank usage with parallele bank alignment usage, but here, there is duplication of the registers description, that is not convenient.


I would like to describe a maximum of information into the register to reflect the correct behaviour, and if possible not duplicating each register 4 times.

Any suggestion is welcome.





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  • 1 month later...

Hello Christian,


The feature you are describing is register aliasing.  The is not supported by IEEE 1685-2009.  It is supported by Accellera SystemRDL 1.0 2009. I would recommend that you have the four registers containing the fields with the appropriate access and modifiedWriteValue. The fact that there is only one physical register is currently beyond IP-XACT.  You can either make a note of this in the description or add vendor extensions to document the relationship.

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  • 1 month later...

I am a member of both the IP-XACT and SystemRDL committees.

The committees are going in different directions with regard to the data model.

IP-XACT documents the interfaces of a design, avoids behavior, and is a communication format for tools.

SystemRDL is all about register hardware and software behavior, and, it is meant as a human design capture format.

The SystemRDL committee is in the process of attempting to add those features of IP-XACT 2009 which are not in SystemRDL 1.0.

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  • 4 months later...

Hello Balasubramamian,

The industry supports SystemRDL.  The Semifore CSRCompiler is the reference platform for the Accellera SystemRDL 1.0 standard and has been supporting the various versions of SystemRDL since 2007. Semifore is a contributing member of the current active Accellera SystemRDL standards committee.

FULL DISCLOSURE:  I work for Semifore, Inc.

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