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What happen if read access is performed on write-only register?


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Hi, All

 

I am curious the guided policy about write-only register.

I am using UVM 1.1d library and refer their guides.

In UVM User Guide : 

5.5 Construncting a Register Model 

Table 7 - Pre-defined Field Access Policies

There is a description as follows :

Access Policy - WO

... Effect of a Read on Current Field Value : No effect.

 

However, In UVM Class Reference

Register Layer > Register Model > Fields > set_access 

There is a description as follows : 

”WO” W: as-is, R: error

It seems the description in above two documents are conflict.

Which one is UVM's intense about write-only register?

Or did I miss the page : above two things are pointing different things?

 

In my opinion, the response on read transaction of write-only field/register have a dependency on Design.

So I think the verification engineer should model the test scenario depend on design specification : The access policy should not limit the operation of design.

 

Thanks,

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You are discussing 2 different things.

(1) What happens when you are reading a WO register or filed.

(2) What happens when you are setting a field in a WO register.

Reading a WO register does not have a dependency on the design.

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