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UART Core not responding on RXD events (Modelsim ASE)

Honored Contributor II

I'm trying to simulate a simple Qsys system with a UART Core (without flow control) in Modelsim ASE environment.  


I modified the self-generated testbench of my top-level Qsys system to realize a loopback between RXD and TXD, the only signals of the exported conduit interface of the core. 


The software simply writes a char and expects to receive it back on RXD (I'm accessing UART Core through common HAL API): this happens correctly on hardware (DE1 board), but doesn't at all in simulation. Here, I can see the correct RXD input of the Qsys system, but UART core doesn't do anything after having received it (so the program execution remains stuck at the "scanf" line). 


I'm attaching my simple test design as a reference. I'm using Quartus II v11.0 design suite. 


Thank you for any help you can give me. 





P.S.: I would also appreciate any suggestions on how to activate the interactive input/output window on Modelsim, for communication with UART Core or even the JTAG UART Core. I tried to set this functionality while istantiating my UART/JTAG UART Core in Qsys but I wasn't able to use it and I couldn't find any alias command for opening the interactive window in the self-generated TCL simulation script, so I thought this is a legacy thing no more available on Qsys.
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