SystemC 24 sc_signal_bool

posedge/negedge

sc_signal_in_if<bool> and sc_signal_in_if<sc_dt::sc_logic> are interfaces that provide additional member functions appropriate for two-valued signals. sc_signal implements these functions:

  1. posedge_event() returns reference to an event that is notified whenever the value of the channel changes and the new value of the channel is true or ‘1’.
  2. negedge_event() returns a reference to an event that is notified whenever the value of the channel changes and the new value of the channel is false or ‘0’.
  3. posedge() returns true if and only if the value of the channel changed in the update phase of the immediately preceding delta cycle and at the current simulation time, and the new value of the channel is true or ‘1’.
  4. negedge() returns true if and only if the value of the channel changed in the update phase of the immediately preceding delta cycle and at the current simulation time, and the new value of the channel is false or ‘0’.

Code



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// Learn with Examples, 2020, MIT license
#include <systemc>
using namespace sc_core;

SC_MODULE(SIGNAL_BOOL) {
  sc_signal<bool> b;
  SC_CTOR(SIGNAL_BOOL) {
    SC_THREAD(writer);
    SC_THREAD(consumer);
    sensitive << b; // triggered by every value change
    dont_initialize();
    SC_THREAD(consumer_pos);
    sensitive << b.posedge_event(); // triggered by value change to true
    dont_initialize();
    SC_THREAD(consumer_neg);
    sensitive << b.negedge_event(); // triggered by value change to false
    dont_initialize();
  }
  void writer() {
    bool v = true;
    while (true) {
      b.write(v); // write to channel
      v = !v; // toggle value
      wait(1, SC_SEC); // write every 1 s
    }
  }
  void consumer() {
    while (true) {
      if (b.posedge()) { // if new value is true
        std::cout << sc_time_stamp() << ": consumer receives posedge, b = " << b << std::endl;
      } else { // if new value is false
        std::cout << sc_time_stamp() << ": consumer receives negedge, b = " << b << std::endl;
      }
      wait(); // wait for any value change
    }
  }
  void consumer_pos() {
    while (true) {
      std::cout << sc_time_stamp() << ": consumer_pos receives posedge, b = " << b << std::endl;
      wait(); // wait for value change to true
    }
  }
  void consumer_neg() {
    while (true) {
      std::cout << sc_time_stamp() << ": consumer_neg receives negedge, b = " << b << std::endl;
      wait(); // wait for value change to false
    }
  }
};

int sc_main(int, char*[]) {
  SIGNAL_BOOL signal_bool("signal_bool");
  sc_start(4, SC_SEC);
  return 0;
}

// Result:
// false->true
0 s: consumer_pos receives posedge, b = 1
// false->true
0 s: consumer receives posedge, b = 1
// true->false
1 s: consumer_neg receives negedge, b = 0
// true->false
1 s: consumer receives negedge, b = 0
// false->true
2 s: consumer_pos receives posedge, b = 1
// false->true
2 s: consumer receives posedge, b = 1
// true->false
3 s: consumer_neg receives negedge, b = 0
// true->false
3 s: consumer receives negedge, b = 0

Reference

Notes Mentioning This Note

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