Processes in SystemC

1. Processes inSystemC Part of HW/SW Codesign of Embedded Systems Course (CE 40-226) Codesign of Embedded Systems

2. Process • Basics • Basic unit of execution within SystemC • Emulate the behavior of target device • Are triggered by clock edges and/or signal expressions • Are not hierarchical • No process can directly call another • Processes communicate through signals Codesign of Embedded Systems

3. ProcessCategories in SystemC • Method process • Thread process • CThread process Codesign of Embedded Systems

4. Method Process • Is called once, when events occur on its sensitivity list • Cannot suspend execution (i.e. wait) • Returns control to the caller (SystemC Kernel) Codesign of Embedded Systems

5. rcv frame id Method Example:Packet Receiver void rcv::extract_id() { frame_type frame; frame = xin;if(frame.type==1) id = frame.ida;else id = frame.idb; } #include “frame.h” SC_MODULE(rcv) { sc_in<frame_type> xin;sc_out<int> id; void extract_id(); SC_CTOR(rcv){ SC_METHOD(extract_id); sensitive(xin); }}; Codesign of Embedded Systems

6. Thread Process • Declaration to SystemC kernel is the same as Method process • Can be suspended and re-activated • wait() system call • Process is re-activated when an event occurs on process SL (Sensitivity List) Codesign of Embedded Systems

7. Thread Example:Traffic Light Controller SC_MODULE(traff) { sc_in<bool> roadsensor;sc_in<bool> clock; sc_out<bool> NSred;sc_out<bool> NSyellow;sc_out<bool> NSgreen;sc_out<bool> EWred;sc_out<bool> EWyellow;sc_out<bool> EWgreen; void control_lights(); Road Sensor SC_CTOR(traff){ SC_THREAD(control_lights); sensitive<<roadsensor;sensitive_pos<<clock; } }; Codesign of Embedded Systems

8. Thread Example:Traffic Light Controller (cont’d) void traff::control_lights() { NSred = NSyellow = false; NSgreen = true; EWred = true; EWyellow = EWgreen = false; while (true) { while (roadsensor.delayed() == false)wait(); NSgreen = false; NSyellow = true; NSred = false; for (i=0; i<5; i++)wait(); NSgreen = NSyellow = false; NSred = true; EWgreen = true; EWyellow = EWred = false; for (i= 0; i<50; i++)wait(); NSgreen = NSyellow = false; NSred = true; EWgreen = false; EWyellow = true; EWred = false; for (i=0; i<5; i++) wait(); Codesign of Embedded Systems

9. The Thread process is the most general one Implementing traff module with Method process requires defining several states Threads are slower than Methods Thread Example:Traffic Light Controller (cont’d) NSgreen = true; NSyellow = NSred = false; EWgreen = EWyellow = false; EWred = true; for (i=0; i<50; i++) wait(); } } Codesign of Embedded Systems

10. Clocked Thread Process • The same as Thread, but is merely sensitive to edge of one clock • Results in better descriptions to synthesize • One major use: Implicit state machine • Implicit state machine vs. Explicit state machine • Additional waiting mechanisms • wait_until(<signal condition>) system call • Process is re-activated when the condition on the signals hold • timed wait, wait until condition with timeout (SystemC 2.0) Codesign of Embedded Systems

11. addr 32 newaddr start data 32 data8 ready datardy Clocked Thread Example:Bus Controller SC_MODULE(bus) { sc_in_clk clock; sc_in<bool> newaddr; sc_in<sc_uint<32> > addr; sc_in<bool> ready; sc_out<sc_uint<32> > data; sc_out<bool> start; sc_out<bool> datardy; sc_inout<sc_uint<8> > data8; sc_uint<32> tdata; sc_uint<32> taddr; void xfer(); Bus Cntrlr Mem Cntrlr SC_CTOR(bus) { SC_CTHREAD(xfer, clock.pos()); datardy = true; } }; Codesign of Embedded Systems

12. Clocked Thread Example:Bus Controller (cont’d) void bus::xfer() { while (true) { wait_until( newaddr.delayed() == true); taddr = addr.read(); datardy = false; data8 = taddr.range(7,0); start = true; wait(); data8 = taddr.range(15,8); start = false; wait(); data8 = taddr.range(23,16); wait(); data8 = taddr.range(31,24); wait(); wait_until(ready.delayed() == true); tdata.range(7,0)=data8; wait(); tdata.range(15,8)=data8; wait(); tdata.range(23,16)=data8; wait(); tdata.range(31,24)=data8; data = tdata; datardy = true; } } Codesign of Embedded Systems

13. What we learned today • Process in SystemC • Methods • Threads • Clocked Threads Codesign of Embedded Systems

14. Complementary notes:Assignments • DON’T FORGETSubscribe to ce226list@ce.sharif.edu by sending an email to majordomo@ce.sharif.edu containing subscribe ce226list in the body. • Today is due date for Assignment 4 • Take Assignment 5Due date: Sat. Ordibehesht 8th Codesign of Embedded Systems

15. Complementary notes:Final Projects • Titles • MP3 Encoder-Decoder • JPEG Encoder-Decoder • TCP/IP Sender-Receiver • ARM7 Processor • TMS32025 DSP • MPEG-2 Encoder • MPEG-2 Decoder • DES/ Tripple-DES/ RSA Encryption-Decryption • Your Suggestion Codesign of Embedded Systems

16. Complementary notes:Final Projects (cont’d) • Today, choose your final project • First Report • Turn in a 1-2 page document of your references • Deadline: Sat. Ordibehesht 8th • Second Report • Prepare a PowerPoint presentation of algorithm or architecture of your design • Deadline: Sat. Ordibehesht 22nd Codesign of Embedded Systems