sc_clock Doubt

[Amol Nikade]

Hi All,

 

I have the below code, I am not understanding how clock instance will get time period/how it will be triggered ?

int sc_main( int, char* [] )
{
    sc_clock      clock;
    dpipe<atom,4> delay("pipe");
    Reader        reader("reader");
    Writer        writer("writer");

    delay.m_clk(clock);

    reader.m_clk(clock);
    reader.m_from_pipe(delay.m_out);

    writer.m_clk(clock);
    writer.m_to_pipe(delay.m_in);

    sc_start(10, SC_NS);

    return 0;
}
 

[Eyck]

sc_clock triggers itself based on the period and the (in your case default) constructor settings. The period is the default_time_unit.

[David Black]

There is no default_time_unit in SystemC; however, the sc_clock default constructor does supply a default value of 1 ns. Be careful you don't set the time resolution larger than 1 ns, if you are going to use the default time. You could of course be more explict:

sc_time clock{ "clock", 1, SC_NS }; //< assumes C++11 or better and using namespace sc_core

 

[Eyck]

Actually there is a default time unit in sc_time.h:

// ----------------------------------------------------------------------------
//  STRUCT : sc_time_params
//
//  Struct that holds the time resolution and default time unit.
// ----------------------------------------------------------------------------

struct SC_API sc_time_params
{
    double time_resolution;		// in femto seconds
    bool   time_resolution_specified;
    bool   time_resolution_fixed;

    sc_time::value_type default_time_unit;		// in time resolution
    bool                default_time_unit_specified;

    sc_time_params();
    ~sc_time_params();
};

Instantiating it you get the default values....

[Philipp A Hartmann]

 

22 hours ago, Eyck said:

Actually there is a default time unit in sc_time.h

 

Looking at the source code of any SystemC implementation is sometimes misleading. Check IEEE 1666-2011, Annex C (deprecated features), item (n):

Quote

n) Default time units and all the associated functions and constructors, including:

1. Function sc_simulation_time
2. Function sc_set_default_time_unit
3. Function sc_get_default_time_unit
4. Function sc_start(double)
5. Constructor sc_clock(const char*, double, double, double, bool)