sc_fifo

sc_fifo is a predefined primitive channel intended to model the behavior of a fifo, that is, a first-in first-out buffer. A fifo is an object of class sc_fifo. Each fifo has a number of slots for storing values. 

The number of slots is fixed when the object is constructed. Default slots size is 16.

sc_fifo has following predefined methods.

• write() : This method write the values passed as an argument into the fifo. If fifo if full then write() function waits till fifo slot is available
• nb_write() : This method is same as write(), only difference is, when fifo is full nb_write() does not wait till fifo slot is avaible. Rather it returns false.
• read() : This method returns the least recent written data in fifo. If fifo is empty, then read() function waits till data is available in fifo.
• nb_read() :This method is same as read(), only difference is, when fifo is empty, nb_read() does not wait till fifo has some data. Rather it returns false.
• num_available() : This method returns the numbers of data values available in fifo in current delta time.
• num_free() : This method returns the number of free slots available in fifo in current delta time.

Example : sc_fifo

  1 #include 

  2

  3 SC_MODULE(example_fifo) {

  4   void example_fifo::m_drain_packets(void);

  5   void example_fifo::t_source1(void);

  6   void example_fifo::t_source2(void);

  7   // Constructor

  8   SC_CTOR(example_fifo) {

  9     SC_METHOD(m_drain_packets);

 10     SC_THREAD(t_source1);

 11     SC_THREAD(t_source2);

 12     // Size the packet_fifo to 5 ints.

 13     sc_fifo<int> packet_fifo (5);

 14   }

 15  

 16   // Declare the FIFO

 17   sc_fifo<int> packet_fifo;

 18 };

 19

 20 void example_fifo::m_drain_packets(void) {

 21   int val;

 22   if (packet_fifo.nb_read(val)) {

 23     std::cout << sc_time_stamp() << ": m_drain_packets(): Received " << val <<

 24       std::endl;

 25   } else {

 26     std::cout << sc_time_stamp() << ": m_drain_packets(): FIFO empty." << std::endl;

 27   }

 28   // Check back in 2ns

 29   next_trigger(2, SC_NS);

 30 }

 31

 32 void example_fifo::t_source1(void) {

 33   int val = 1000;

 34   for (;;) {

 35     wait(3, SC_NS);

 36     val++;

 37     packet_fifo.write(val);

 38     std::cout << sc_time_stamp() << ": t_thread1(): Wrote " << val << std::endl;

 39   }

 40 }

 41

 42 void example_fifo::t_source2(void) {

 43   int val = 2000;

 44   for (;;) {

 45     wait(5, SC_NS);

 46     val++;

 47     packet_fifo.write(val);

 48     std::cout << sc_time_stamp() << ": t_thread2(): Wrote " << val << std::endl;

 49   }

 50 }

 51

 52 int sc_main(int argc, char* argv[]) {

 53   example_fifo ex_fifo ("ex_fifo0");

 54   sc_start(30, SC_NS);

 55   return 0;

 56 }

Simulation Output : sc_fifo

0 s: m_drain_packets(): FIFO empty.

 2 ns: m_drain_packets(): FIFO empty.

 3 ns: t_thread1(): Wrote 1001

 4 ns: m_drain_packets(): Received 1001

 5 ns: t_thread2(): Wrote 2001

 6 ns: m_drain_packets(): Received 2001

 6 ns: t_thread1(): Wrote 1002

 8 ns: m_drain_packets(): Received 1002

 9 ns: t_thread1(): Wrote 1003

 10 ns: m_drain_packets(): Received 1003

 10 ns: t_thread2(): Wrote 2002

 12 ns: m_drain_packets(): Received 2002

 12 ns: t_thread1(): Wrote 1004

 14 ns: m_drain_packets(): Received 1004

 15 ns: t_thread1(): Wrote 1005

 15 ns: t_thread2(): Wrote 2003

 16 ns: m_drain_packets(): Received 1005

 18 ns: m_drain_packets(): Received 2003

 18 ns: t_thread1(): Wrote 1006

 20 ns: m_drain_packets(): Received 1006

 20 ns: t_thread2(): Wrote 2004

 21 ns: t_thread1(): Wrote 1007

 22 ns: m_drain_packets(): Received 2004

 24 ns: m_drain_packets(): Received 1007

 24 ns: t_thread1(): Wrote 1008

 25 ns: t_thread2(): Wrote 2005

 26 ns: m_drain_packets(): Received 1008

 27 ns: t_thread1(): Wrote 1009

 28 ns: m_drain_packets(): Received 2005

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