Error: (E112) get interface failed: port is not bound - SystemC - c++

Question

My goal is to create an ALU that adds and subtracts with a barrelshifter
alu.h
#include "systemc.h"
SC_MODULE(alu){
sc_in<bool> op;
sc_in<sc_int<8> > a;
sc_inout<sc_int<8> > b;
sc_out<sc_int<8> > output;
void alu_method();
SC_CTOR(alu) {
SC_METHOD(alu_method);
dont_initialize();
sensitive << a,b,op;
}
};
alu.cpp
#include "alu.h"
void ALU::alu_method(){
if (op.read() == 0){
//substract
out.write(in.read() - in_bs.read());
}
else{
//add
out.write(in.read() + in_bs.read());
}
}
barrelshift.h
#include <systemc.h>
void make_barrel();
SC_MODULE(barrel_shift) {
sc_in<bool> clk;
sc_in<bool> enable;
sc_in<bool> left_right;
sc_in<sc_uint<3> > shift_amt;
sc_in<sc_int<8> > din;
sc_inout<sc_int<8> > dout;
void barrel_method();
SC_CTOR(barrel_shift) {
SC_METHOD(barrel_method);
dont_initialize();
sensitive << clk.pos(); //edge sensitive
}
};
barrelshift.cpp
#include "barrelshift.h"
void barrel_shift :: barrel_method(){
if(enable.read() == 1){
if(left_right.read() == 0){ //shift left
dout.write(din.read() << shift_amt.read());
}else if(left_right.read() == 1){ // right shift
dout.write(din.read() >> shift_amt.read());
}
}
else
cout << "Not enabled "<<endl;
dout <= din;
}
sc_main.cpp
#include <systemc.h>
#include "alu.h"
#include "barrelshift.h"
int sc_main(int argc, char* argv[]){
sc_trace_file *tf;
//Signals
sc_signal <bool> enable, op, l_r;
sc_signal <sc_int<8> > a, output,b, bin;
sc_signal < sc_uint<3> > shift_amt;
//Clock
sc_clock clk("clk",10,SC_PS,0.5);
alu myALU("myALU");
barrel_shift myShifter("myShifter");
myALU.a(a);
myALU.b(b);
myALU.output(output);
myALU.op(op);
myShifter.clk(clk);
myShifter.din(bin);
myShifter.enable(enable);
myShifter.left_right(l_r);
myShifter.shift_amt(shift_amt);
myShifter.dout(b);
tf = sc_create_vcd_trace_file("trace_file");
sc_trace(tf, clk, "clk");
sc_trace(tf, a, "a");
sc_trace(tf, bin, "BarrelShifter In");
sc_trace(tf, op, "op");
sc_trace(tf, shift_amt, "shift_amt");
sc_trace(tf, l_r, "left_right");
sc_trace(tf, enable, "enable");
sc_trace(tf, b, "b");
sc_trace(tf, output, "output");
sc_close_vcd_trace_file(tf);
cout << "The result from the ALU is: " << output.read();
}
There are no errors when I build it. But whenever I try to execute it, I get the following error:
Error: (E112) get interface failed: port is not bound: port 'myALU.port_0' (sc_in)
In file: sc_port.cpp:231
What is causing this and how can I fix it?

Answer 1

The error message
Error: (E112) get interface failed: port is not bound: port 'myALU.port_0' (sc_in)
means that the port myALU.port_0 is not bound to a signal. But which port in the alu module corresponds to port_0?
It is good practice to name all ports and signals -- regardless of the type of hardware description language you are using -- to make errors like this easier to diagnose.
Name the ports in the alu constructor:
SC_CTOR(alu) :
op("op"),
a("a"),
b("b"),
output("output")
{
// ...
I couldn't reproduce the error you were seeing. I saw this error (after providing names for all ports and signals):
Error: (E115) sc_signal<T> cannot have more than one driver:
signal `signal_5' (sc_signal)
first driver `myShifter.dout' (sc_inout)
second driver `myALU.b' (sc_inout)
I noticed some other problems in your code:
Your code doesn't compile because the wrong variable names are used in alu_method().
sc_start() is not called in sc_main().
There is an invalid sensitive call in alu() -- should be sensitive << a << b << op;

Answer 2

The problem was with the sensitivity list for alu. It should have been:
sensitive << a << b << op;

Answer 3

As noted correctly by #DarrylLawson, this error message indicates that the the port myALU.port_0 is not bound to a signal (and you would get a clearer name if you had given the port a name in the constructor).
An important nuance imho is that it means the port is not bound to a signal at the time the error is given. You may have code that binds it, but this is only executed at some point during elaboration. If you try to use the port before that (e.g. inside the constructor of your module), you can still get this error message. In that case the error would occur at time 0.