SystemC 12 Sensitivity
Sensitivity
The sensitivity of a process instance is the set of events and time-outs that can potentially cause the process to be resumed or triggered. A process instance is said to be sensitive to an event if the event has been added to the static sensitivity or dynamic sensitivity of the process instance. A time-out occurs when a given time interval has elapsed.
Two types of sensitivities
- Static sensitivity is fixed during elaboration, supported with a sensitivity list for each process in a module.
-
Dynamic sensitivity may vary over time under the control of the process itself, support with
- wait() for a thread, or
- next_trigger() for a method.
Note:
-
wait(): wait on events in sensitivity list (SystemC 1.0).- Need to add a sensitivity list
sensitive << e1 << e2;in the module constructor (eg.SC_CTOR)
- Need to add a sensitivity list
Code
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// Learn with Examples, 2020, MIT license
#include <systemc>
using namespace sc_core;
SC_MODULE(SENSITIVITY) {
sc_event e1, e2; // events for inter-process triggering
SC_CTOR(SENSITIVITY) {
SC_THREAD(trigger_1); // register processes
SC_THREAD(trigger_2);
SC_THREAD(catch_1or2_dyn);
SC_THREAD(catch_1or2_static);
sensitive << e1 << e2; // static sensitivity for the preceeding process, can only "OR" the triggers
}
void trigger_1() {
wait(SC_ZERO_TIME); // delay trigger by a delta cycle, make sure catcher is ready
while (true) {
e1.notify(); // trigger e1
wait(2, SC_SEC); // dynamic sensitivity, re-trigger after 2 s
}
}
void trigger_2() { // delay trigger by a delta cycle
wait(SC_ZERO_TIME);
while (true) {
e2.notify(); // trigger e2
wait(3, SC_SEC); // dynamic sensitivity, re-trigger after 3 s
}
}
void catch_1or2_dyn() {
while (true) {
wait(e1 | e2); // dynamic sensitivity
std::cout << "Dynamic sensitivty: e1 or e2 @ " << sc_time_stamp() << std::endl;
}
}
void catch_1or2_static(void) {
while (true) {
wait(); // static sensitivity
std::cout << "Static sensitivity: e1 or e2 @ " << sc_time_stamp() << std::endl;
}
}
};
int sc_main(int, char*[]) {
SENSITIVITY sensitivity("sensitivity");
sc_start(7, SC_SEC);
return 0;
}
// Result:
// e1 triggered at 0, 2, 4, 6 s;
// e2 triggered at 0, 3, 6 s
// e1 or e2
Static sensitivity: e1 or e2 @ 0 s
// e1 or e2
Dynamic sensitivty: e1 or e2 @ 0 s
// e1 or e2
Static sensitivity: e1 or e2 @2 s
// e1 or e2
Dynamic sensitivty: e1 or e2 @2 s
// e2
Static sensitivity: e1 or e2 @3 s
// e2
Dynamic sensitivty: e1 or e2 @3 s
// e1
Static sensitivity: e1 or e2 @4 s
// e1
Dynamic sensitivty: e1 or e2 @4 s
// e1 or e2
Static sensitivity: e1 or e2 @6 s
// e1 or e2
Dynamic sensitivty: e1 or e2 @6 s