SystemC 23 Resolved Signal
Resolved signal
is an object of class sc_signal_resolved or class sc_signal_rv. It differs from sc_signal in that a resolved signal may be written by multiple processes, conflicting values being resolved within the channel.
-
sc_signal_resolvedis a predefined primitive channel derived from classsc_signal. -
sc_signal_rvis a predefined primitive channel derived from classsc_signal.- a)
sc_signal_rvis similar tosc_signal_resolved. - b) The difference is that the argument to the base class template
sc_signalis typesc_dt::sc_lv<W>instead of typesc_dt::sc_logic.
- a)
Class definition of sc_signal_resolved/rv
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// sc_signal_resolved
class sc_signal_resolved:
public sc_signal<sc_dt::sc_logic,SC_MANY_WRITERS>
// sc_signal_rv
template <int W> class sc_signal_rv:
public sc_signal<sc_dt::sc_lv<W>,SC_MANY_WRITERS>
Resolution table for sc_signal_resolved
| 0 | 1 | Z | X | |
|---|---|---|---|---|
| 0 | 0 | X | 0 | X |
| 1 | X | 1 | 1 | X |
| Z | 0 | 1 | Z | X |
| X | X | X | X | X |
In short, a resolved signal channel can be written by multiple processes at the same time. This differs from an sc_signal, which can only be written by one process at each delta cycle.
Code
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// Learn with Examples, 2020, MIT license
#include <systemc>
#include <vector> // use c++ vector lib
using namespace sc_core;
using namespace sc_dt; // sc_logic defined here
using std::vector; // use namespace for vector
SC_MODULE(RESOLVED_SIGNAL) {
sc_signal_resolved rv; // a resolved signal channel
vector<sc_logic> levels; // declares a vector of possible 4-level logic values
SC_CTOR(RESOLVED_SIGNAL) : levels(vector<sc_logic>{sc_logic_0, sc_logic_1, sc_logic_Z, sc_logic_X}){ // init vector for possible 4-level logic values
SC_THREAD(writer1);
SC_THREAD(writer2);
SC_THREAD(consumer);
}
void writer1() {
int idx = 0;
while (true) {
rv.write(levels[idx++%4]); // 0,1,Z,X, 0,1,Z,X, 0,1,Z,X, 0,1,Z,X
wait(1, SC_SEC); // writes every 1 s
}
}
void writer2() {
int idx = 0;
while (true) {
rv.write(levels[(idx++/4)%4]); // 0,0,0,0, 1,1,1,1, Z,Z,Z,Z, X,X,X,X
wait(1, SC_SEC); // writes every 1 s
}
}
void consumer() {
wait(1, SC_SEC); // delay read by 1 s
int idx = 0;
while (true) {
std::cout << " " << rv.read() << " |"; // print the read value (writer1 and writer2 resolved)
if (++idx % 4 == 0) { std::cout << std::endl; } // print a new line every 4 values
wait(1, SC_SEC); // read every 1 s
}
}
};
int sc_main(int, char*[]) {
RESOLVED_SIGNAL resolved("resolved");
sc_start(17, SC_SEC); // runs sufficient time to test all 16 resolve combinations
return 0;
}
// Result:
// consumer2 == 0, consumer1 = 0, 1, Z, X
0 | X | 0 | X |
// consumer2 == 1, consumer1 = 0, 1, Z, X
X | 1 | 1 | X |
// consumer2 == Z, consumer1 = 0, 1, Z, X
0 | 1 | Z | X |
// consumer2 == X, consumer1 = 0, 1, Z, X
X | X | X | X |