Accessing a c variable in modelsim

[rayan123]

I am using modelsim to simulate a DPI files and want to access a variable from a c file. I am not sure if i can do that. I tried to find the command for this but could not. Is it possible, if so what is the command.

Thanks in advance

 

[dave_59]

If you mean you want to access a Verilog/SystemVerilog variable from a C file, you cannot do it directly. You can either export a SV function that returns the value of the variable you want to access(preferred), or you can write VPI routines to access the variable.

- - - Updated - - -

After reading the title of your post again, it seems you want to access a C variable from Modelsim. You can do this with the properly licensed version of Modelsim/Questa that supports C debug. See the C debug section of the User Manual.

Or maybe you meant you want to access a C variable from SystemVerilog. You can't do that directly either. You would have to import a C method that does the access for you.

 

[rayan123]

Hi Dave,

Thanks for the reply.

What i meant was, is it possible to add c variables from system verilog into questasim wave, so that i can see how that c variable is changing its value at different clock edges

Regards,
Rayan

 

[dave_59]

You can't do that. Your C code is compiled by a generic C compiler and does not produce "update" events when someone writes to a variable. As I said, you would need to either call a C DPI function that polls the C variable at each clock cycle, or export a SV function that sets an SV variable that you can add to the wave window. There might be other ways depending on how your DPI code executes.