1. Real-Time Systems time dependent control oriented driven by events rather than data

2. Control Flow Diagram extension to data flow diagram to represent control flow rather than data flow contains same processes as the data flow diagram but instead of showing data flow, it diagrams control flow diagram the events that cause the various process to be activated

3. Control Flow Diagram (2) together with the CSPEC (control specification) show – how software behaves when the event or control signal is sensed – which processes are invoked as a consequence of the occurrence of the event

4. Control Flow Diagram (3) control item window into CSPEC

5. Drawing a Control Flow Diagram draw the data flow diagram and remove all of the data flow arrows add control items and windows into CSPEC where needed

6. A Data Flow Process Bubble current temperature safe point temperature check temperature status

7. PSPEC for check temperature If current temperature> safe temperature then set status to “true”; else set status to “false”; end if;

8. Control Flow Diagram for check temperature check temperature above safepoint

9. Data Flow for Copier read op input manage copying produce user displays reload paper perform problem diagnosis op commands and data copy info copy status displays reload reqs. reload status problem type problem indicator

10. Copier Events start/stop paper feed (jammed, empty, etc.) finished

11. Control Flow for Copier read op input manage copying produce user displays reload paper perform problem diagnosis start/stop paper feed status alarm full finished

12. Determining Events list all sensors that are read by software list all interrupt conditions list all switches activated by operator list all data conditions look at noun-verb combinations reviewing control items as possible CSPEC I/Os identify states, how each state is reached, & define transitions between states

13. Microwave Oven Events Half Power -- user pressed Full Power -- user pressed Timer -- user set Door open -- switch not closed Door Closed -- switch is closed Start -- user pressed Timeout -- timer has finished

14. Control Flow Diagram and CSPEC event that flows from the outside world into | (CSPEC) implies the CSPEC will activate one or more processes in the CFD A control item that emanates from a process and flows into | (CSPEC) implies control and activation of some other process or outside entity

15. Events events occur at discrete points in time and cause an instantaneous change in the state of a process can occur asynchronously (any point in time) or synchronously (at clocked intervals)

16. State Transition Diagrams graphical representation of the events and the stimuli that cause transition from one event to another above each transition list the input/output that cause/result from the stimuli and event.

17. State Transition Diagrams possible state possible transition between states

18. State Transition Matrix uses a tabular rather than graphical form all possible states identify the rows all stimuli identify the columns at intersection next possible state is listed add column at end of matrix for outputs

22. IDLE DIAL TONE RINGING DISTIN. DIAL TONE BUSY ON HOOK/QUIET DIAL BUSY NUMBER/ BUSY TONE CALLED PARTY OFF HOOK/ CONNECTED DIAL IDLE NUMBER/ RING BACK TONE DIAL IDLE NUMBER/ RING BACK TONE DIAL BUSY NUMBER/ BUSY TONE ON HOOK/QUIET OFF HOOK/DIAL TONE ON HOOK/QUIET DIAL 9/ DISTINCTIVE DIAL TONE

24. The state diagram depends on the range of facilities on the CD player. Idle Door Close Ready Disk Door open Disk Door open Ready to play Ready to play Idle Disk playing Disk playing Track selection Track selection Off button On button Door closed Off button Open door Door open Door closed End of play Play button Off button Track selector Play button

27. Microwave Oven Events Half Power -- user pressed Full Power -- user pressed Timer -- user set Door open -- switch not closed Door Closed -- switch is closed Start -- user pressed Timeout -- timer has finished

29. Idle Full power on Full power on Half power on Half power on Set time Set time Operation disabled Operation disabled Operation enabled Operation enabled Timed operation Timed operation Cooking complete Cooking complete Idle Timer Full Power Full Power Half Power Half Power Door open Door open Door closed Door closed Start Timeout