Error: (E112) get interface failed: index out of range: port 'mux.port_0' (sc_in)

[Hrishikesh]

Hi,

I am new to system c and in the process of exploring I am facing below Issue please help me out in finding out the root cause.

Error: (E112) get interface failed: index out of range: port 'mux.port_0' (sc_in)
In file: ../../../src/sysc/communication/sc_port.cpp:235
 

//----------------------------------------------------------------------
// 4 TO 1 Multiplexer
//----------------------------------------------------------------------

#include "systemc.h"

SC_MODULE(mux_4_to_1){

  // Port Decleration
  sc_in<sc_bv<4>> i_i; // 4-Bit Input
  sc_in<sc_bv<2>> s_i; // 2-Bit Select Line
  sc_out<bool> y_o; // Output
  
  // Multiplexer Logic
  void mux(){
    
    // Convert bit vector to int
    int select_value = s_i.read().to_uint();
    
    switch(select_value){
      case 0  : y_o.write(i_i[0]);
                   break;
      case 1  : y_o.write(i_i[1]);
                   break;
      case 2  : y_o.write(i_i[2]);
                   break;
      case 3  : y_o.write(i_i[3]);
                   break;
      default : y_o.write(false);
    }
  }

  // Constructor
  SC_CTOR(mux_4_to_1){
    SC_METHOD(mux);
    sensitive <<i_i <<s_i;
  }

};

 

//----------------------------------------------------------------------
// 4 TO 1 Multiplexer Driver
//----------------------------------------------------------------------

#include "systemc.h"

SC_MODULE(driver){ 
  
  // Signals to be driven
  sc_out<sc_bv<4>> i_i;
  sc_out<sc_bv<2>> s_i;
  
  // Function to apply inputs
  void inputs(){
    i_i.write("0010");

    s_i.write("00");
    wait(5,SC_NS);

    s_i.write("01");
    wait(5,SC_NS);

    s_i.write("10");
    wait(5,SC_NS);

    s_i.write("11");
    wait(5,SC_NS);
  }
  
  // Constructor
  SC_CTOR(driver){
    SC_THREAD(inputs);
    sensitive <<i_i <<s_i;
  }
};

 

//----------------------------------------------------------------------
// 4 TO 1 Multiplexer Driver
//----------------------------------------------------------------------

#include "systemc.h"

SC_MODULE(monitor){
  
  // Signals to be monitored
  sc_in<sc_bv<4>> i_i;
  sc_in<sc_bv<2>> s_i;
  sc_in<bool> y_o;
  
  // Function to monitor signals
  void mon(){
    cout << "Input: "<<i_i.read() << "Select:" <<s_i.read() << " Output: "<<y_o.read() <<endl;
  }
  
  // Constructor
  SC_CTOR(monitor){
    SC_METHOD(mon);
    sensitive <<i_i <<s_i <<y_o;
  }
};

 

//----------------------------------------------------------------------
// 4 TO 1 Multiplexer Main
//----------------------------------------------------------------------

#include "systemc.h"
#include "mux_4_to_1.h"
#include "driver.h"
#include "monitor.h"

// Main Function
int sc_main( int argc, char* argv[]){
  sc_signal <sc_bv<4>> i_i;
  sc_signal <sc_bv<2>> s_i;
  sc_signal <bool> y_o;

  mux_4_to_1 mux("mux");
  driver drive("driver");
  monitor mon("monitor");
  mux.i_i(i_i); mux.s_i(s_i); mux.y_o(y_o);
  drive.i_i(i_i); drive.s_i(s_i);
  mon.i_i(i_i); mon.s_i(s_i); mon.y_o(y_o);

  //Waveform
  sc_trace_file *Tf;
  Tf = sc_create_vcd_trace_file("traces");
  sc_trace(Tf, i_i, "i_i");
  sc_trace(Tf, s_i, "s_i");
  sc_trace(Tf, y_o, "y_o");
  sc_start(30,SC_NS);
  sc_close_vcd_trace_file(Tf);
  return 0; 
}

Thank you in advance,

I want some suggestions and guidance from the community to ramp up my learning journey.

[Eyck]

Actually you try to call an array operator for the port i_i in mux_4_to_1. This does not access the respective bit in the data but the n-th interface of a (potential) multi-port. So you need to do a explcit read to the the sc_bit and then an array access:

  // Multiplexer Logic
  void mux(){
    
    // Convert bit vector to int
    int select_value = s_i.read().to_uint();
    auto in_val = i_i.read();
    switch(select_value){
      case 0  : y_o.write(in_val[0]);
                   break;
      case 1  : y_o.write(in_val[1]);
                   break;
      case 2  : y_o.write(in_val[2]);
                   break;
      case 3  : y_o.write(in_val[3]);
                   break;
      default : y_o.write(false);
    }
  }

There are several other things to your code:

• You should use C++11
• You should name your ports and signals. Using C++11 this would look like

  sc_out<sc_bv<4>> i_i{"i_i"};

  This eases debugging (and tracing).
• sc_main should only instantiate the toplevel module/testbench. No structural code and no signals in sc_main. This eases reuse of modules and porting it to other simulators (Synopsys, SiemensEDA, or Cadence). The only other code should be paring command line arguments, setting up tracing/logging, starting simulation and evaluating the results. It also unifies your sc_main across different models.
• Maros SC_CTOR and SC_MODULE are discuraged and, as far as I know, will be deprecated and removed from future standards. The do not add substantial functionality.

[Hrishikesh]

Thank you for taking time to go through the code and pointing out the problem, also thank you for your valuable suggestions.

I also had to explicitly convert the read value to bool before writing it to output.
 

// Multiplexer Logic
  void mux(){
    
    // Convert bit vector to int
    int select_value = s_i.read().to_uint();
    sc_bv<4> in = i_i.read();
    
    switch(select_value){
      case 0  : y_o.write(in[0].to_bool());
                   break;
      case 1  : y_o.write(in[1].to_bool());
                   break;
      case 2  : y_o.write(in[2].to_bool());
                   break;
      case 3  : y_o.write(in[3].to_bool());
                   break;
      default : y_o.write(false);
    }
  }

 

I have limited knowledge in filed of system level design, but how modules will be designed if SC_MODULE macro is discontinued.

[AmeyaVS]

Hello @Hrishikesh,

You can always see how the SC_MODULE macro is expanded.

One can run the source through pre-processor stage of the compiler to see the actual code.

SystemC is C++ Library, i.e. these macros are there for convenience to succinctly capture the model intent.

One can easily forgo them and usually recommended approach is to usually avoid them.

Hope it helps.

Regards,

Ameya Vikram Singh