Automatically Verifying the RTL - 2024.1 English

C/RTL co-simulation uses a C test bench, running the main() function, to automatically verify the RTL design running in behavioral simulation. The C/RTL verification process consists of three phases:

1. The C simulation is executed and the inputs to the top-level function, or the Design-Under-Test (DUT), are saved as “input vectors.”
2. The “input vectors” are used in an RTL simulation using the RTL created by C synthesis in Vivado simulator, or a supported third-party HDL simulator. The outputs from the RTL, or results of simulation, are saved as “output vectors.”
3. The “output vectors” from the RTL simulation are returned to the main() function of the C test bench to verify the results are correct. The C test bench performs verification of the results, in some cases by comparing to known good results.

The following messages are output by the Hls compiler as verification progresses:

While running C simulation:

INFO: [COSIM 212-14] Instrumenting C test bench ...
   Build using ".../bin/g++"
   Compiling dct_test.cpp_pre.cpp.tb.cpp
   Compiling dct_inline.cpp_pre.cpp.tb.cpp
   Compiling apatb_dct.cpp
   Generating cosim.tv.exe
INFO: [COSIM 212-302] Starting C TB testing ... 
Test passed !

At this stage, because the C simulation was executed, any messages written by the C test bench will be output to the Console window and log file.

While running RTL simulation:

INFO: [COSIM 212-333] Generating C post check test bench ...
INFO: [COSIM 212-12] Generating RTL test bench ...
INFO: [COSIM 212-1] *** C/RTL co-simulation file generation completed. ***
INFO: [COSIM 212-323] Starting verilog/vhdl simulation. 
INFO: [COSIM 212-15] Starting XSIM ...

At this stage, any messages from the RTL simulation are output in console window or log file.

While checking results back in the C test bench:

INFO: [COSIM 212-316] Starting C post checking ...
Test passed !
INFO: [COSIM 212-1000] *** C/RTL co-simulation finished: PASS ***

The following are requirements of C/RTL co-simulation:

• The test bench must be self-checking as described in Writing a Test Bench, and return a value of 0 if the test passes or returns a non-zero value if the test fails.
• Co-simulation Requirements for Interface Synthesis must be met.
• Any arrays or structs on the design interface cannot use the optimization directives listed in Unsupported Optimizations for Co-Simulation.
• Any third-party simulators must be available in the search path to be launched by the Vitis unified IDE or vitis-run command.
• If a third-party simulator is used the IP simulation libraries must be compiled for use with third-party simulators as described in Simulating IP Cores.