IP-XACT addressBlock vs SystemRDL addrmap/regfile

[amal.khailtash]

Sorry, but this question is related to SystemRDL, but there is no discussion board for that, so I post here that is the closest.

IP-XACT addressBlock has a range attribute that I can define and leave some space at the end of the addressBlock.  I would like to do something similar in SystemRDL.  I tried defining a regfile (no associated a top-level RTL), but I cannot see an equivalent range attribute.  Then I thought about using an addrmap (although it has an associated RTL view), but again that one does not have a range attribute either!

How do I leave some reserved space at the end of an addrmap or a regfile?  If I had an element after the last register, I could leave some space.  But not sure what to do at the end?  Note that this regfile is meant to be instantiated in various other addrmaps and need to have a specific range.  Is there such a thing as a null register?  Maybe I should declare a register array with no access "sw = na" attribute?

[Richard Weber]

Hello Amal,

There is no provision in SystemRDL to reserve space, and I agree that this is a limitation of the SystemRDL standard. The SystemRDL components addrmap and regfile are sized to the minimum required by their content.  In general authors reserve space by placing offsets on the instances following the component instance.  If you are using array instances you can also use the stride feature on the array instance to leave gaps between the array members. Often designs have extra registers to facilitate design corrections after release to manufacturing. If your design has this kind of register perhaps, they could have offsets specified to force the regfile to be larger. Otherwise, I would avoid extra registers, since they show up in documentation, header files, and RTL implementation.

 

Rich