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ljepson74

TLM transaction w/o a transaction type? (or w/ simple transaction type, like just "int")

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We are using TLM to pass transactions from SystemVerilog to SystemC.

I have two cases where I am stuck.  Actually, it is the same case, but I have two angles to my question.

 

1) Is it possible to still use a TLM setup, but without a transaction type.  (I realize that this is contradictory to the acronym.)  A c-model has a debug function which takes no input arguments.  So, when the SV testbench runs into a problem, it can call this function in the SystemC/c-model.  As all of our connections now are sc_port/sc_export, with TLM, I'd like to stick with that flow if possible, rather than adding DPIs/VPIs/(PLIs) or any other mechanism to communicate between languages.  However, since the function has no input arguments, I don't need a transaction type.   So, is there a way to do a TLM call without a transaction type?  (I suppose I could just use another transaction type and ignore the data.)

 

2) Imagine the above c-model input function that takes no input arguments.  Let's say now that the c-model function takes a single integer as its input.  So, now I do have a transaction type, but a very simple one.  It seems like overkill, but do I still need to define matching .h and .svh (that extends uvm_sequence_item) transcation types and the related do_pack, do_unpack, etc. routines?   It seems like overkill.  I suspect that I must, if I want to use TLM.

(Given that the answer to this question must be, yes, does anyone out there just use a generic grab-bag transaction type for cases like this?)

 

//my thought of passing a transaction which is just an int

in sv tb:

   uvm_blocking_put_port #(int)  sb_debug_call1_to_cmodel;

in sc c-model

   public tlm::tlm_blocking_put_if<sc_int <32>>     //or smthg like that

 

 

Any thoughts?  I know I just need to refresh myself on DPIs, but answers to the above question are welcome.

 

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hello,

 

#1

>I suppose I could just use another transaction type and ignore the data.

yes this is the simple path. you have to provide a transaction type and you have to pass "something". i agree sticking with one path is the better option and TLM is a better path since its an abstract interface without being tied directly to an implementation/language/domain ...

 

#2 

TLM (from the sv impl side) allows you use non-uvm_objects as transactions. so you can pass ints, enum, structs as transaction without wrapping them. if the base types are supported by code mediating between SV/SC depends upon your implementation.

 

nevertheless you should be aware that when you use primary types (int,enum,string,structs,...) as transaction objects in uvm-sv you basically have a pass-by-value semantic. if you pass traditionally objects around you have a pass-by-reference semantic. 

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Thanks a lot, Uwes.  That helps.  As a simple/quick solution, I think I am going with #1 (and a clear note that the transaction type is mostly irrelevant, so as not to confuse whomever inherits my code).  I tried #2 and ran into some trouble.  If I explore it (#2) more and am still stuck, I'll post here. 

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