Validation of Communications Systems with SDL phần 4 docx

Interactive Simulation 83

A. Return to the previous simulation step by pressing the undo Simulator button.

B. In the Simulator, select the transition38 trans dlca!dlc(1): from waitua input t320 : as shown

in Figure 4.46, the Editor displays in bold the corresponding input (T320). In the ELSE

branch, you see the output of DLCstopped, which caused the problem.

Figure 4.46 Searching for the unexpected signal bug

C. In the Editor, select Navigate > Up: the block type V76 DLC is now displayed, as in

Figure 3.12; you see that signal DLCstopped goes to process dispatch, through the signal

route DLCs.

D. In the Editor, select process dispatch and do Navigate > Down and Navigate > Next

Partition: you see that under state waitUA, the input of signal DLCstopped is missing.

4.3.3.3 Correct the bug

You will add the missing input of signal DLCstopped under state waitUA in process dispatch.

A. When the Simulator is running, the Editor prevents you from modifying the SDL model:

exit from the Simulator (answering No to the question) to enable the modification features

of the Editor. Do not exit from the Editor.

38 The firable transition trans dlca!dlc(1): from waitua input t320 is preceded by a *: it reminds you that you executed

it before the undo.

84 Validation of Communications Systems with SDL

B. In Windows (or Unix), make a copy of the file v76.pr into v76 v1.pr (but continue working

on v76.pr, which becomes version 2).

C. In process dispatch, partition part2, select the input of DLCstopped under state ready,

copy it, select the state waitUA and paste: the whole transition is inserted, as shown in

Figure 4.47.

waitUA

V76frame

(V76para)

V76para ! present

UA

V76frame(V76para)

TO DLCs(V76para

! UA ! DLCi)

ready

ELSE

-

DLCstopped

(DLCnum)

L_ReleaseInd(DLCnum)

DLCs(DLCnum):= NULL

ready

Figure 4.47 Missing input of signal DLCstopped added under state waitUA

D. In the pasted transition, don’t forget to change the nextstate - into nextstate ready, otherwise

you will be stuck in state waitUA.

E. Save the SDL model.

4.3.3.4 Simulate to check the bug correction

To check that the bug has been corrected, you will load and automatically replay the scenario

stored in Section 4.3.3.1. See Section 4.3.1 for details on restarting the Simulator.

A. In the SDL Editor, unload all files except v76.pr.

B. If the ObjectGeode Launcher is not running, in the Editor select Tools > SDL & MSC

Simulator.

C. In the ObjectGeode Launcher, Press the Build button, then if you do not get any SDL errors,

press the Execute button.

D. The Simulator starts: press on SDL Tracking and on Start MSC.

E. In the Editor, close all windows except Default tracking and ogsm4, close the Framework

view and select Window > Tile Horizontally, to obtain the screen shown in Figure 4.38.

F. In the Simulator, select File > Scenario > Load, and open retry1.scn: after end of scenario

loading, you see 0/26 in the lower part of the Simulator, as shown in Figure 4.48: it means

that you are at Step 0, and the loaded scenario has 26 steps.

G. Press the button All located under Redo: (or press 26 times the redo Simulator button):

when you see end of scenario execution and 26/26, it means that the scenario loaded from

the file retry1.scn has been replayed entirely39.

39 If the scenario does not replay until the end, check that your feeds are loaded: see Section 4.3.1.4.

Interactive Simulation 85

Figure 4.48 The current and maximum step numbers after loading the scenario

H. The bottom of the MSC generated by the Simulator looks like Figure 4.49(a): the signal

dlcstopped has been transmitted, but it is in the queue of process dispatch.

dlcstopped(0) dlcstopped(0)

(a) (b)

Figure 4.49 MSC trace: signal dlcstopped in the process queue (a) and consumed (b)

I. To watch the input FIFO queues of the model, press the Watch... button; in the Watch

creation window, press Queues: as depicted in Figure 4.50, a watch window appears, dis￾playing the contents of the queues. As expected, you can see the signal dlcstopped in the

queue of process dispatch.

first signal in the queue

signal name

signal parameter value

empty queue

Figure 4.50 Watching the input queues

J. In the Simulator, double-click the transition

trans dlca!dispatch : from_waitua_input_dlcstopped

the signal dlcstopped disappears from the watch and the MSC shows a filled arrowhead as

in40 Figure 4.49(b).

We have returned to the initial model state, from where we can simulate other scenarios.

40 The arrow is inclined, because the actual input of dlcstopped (the arrowhead) occurred after the process stop (the X

symbol). A horizontal arrow would mean output dlcstopped, followed by input dlcstopped and then by process stop,

which is not the actual behavior.