ge Show Trace Breakpoint Help Execute Group Welcome to the SDL SIMULATOR. Simulating sy Symbol Break Command : Transition Until Timer Send Signal Group Send To Send Via Send None Examine Group Process List Variable Var In Scope Trace Group Command Figure 4.5 The Simulator is ready PROCESS TYPE to Peer ready V76frame ready (V76par) Figure 4.6 SDL trace: start symbol ready to be executed C. In the Simulator, select View > Command Window: the Command Window appears, as shown in Figure 4.7; in its upper part you can see the ready queue of the Simulator, where three process instances are ready to be executed: BtoA, dispatch in block DLCa and dispatch in block DLCb. D. In the Simulator, press the button Transition three times: the ready queue is now empty. If you press Transition again, the Simulator displays No process instance scheduled for a transition: the simulation is blocked because the SDL model now expects to receive some external signals. 4.2.1.4 Prepare the Simulator for MSC recording A. In the Simulator, type the command Define-MSC-Trace-Channels on (or type d-m-t-c on): instead of drawing only one environment instance, the Simulator will generate one envi- ronment instance for each external SDL channel: DLCaSU and DLCbSU, as shown in Figure 4.8. This clarifies the MSC trace, separating signals linked to DLCs A and B. In the Simulator, select Trace > MSC Trace: Start: a Select window appears. 44 Validation of Communications Systems with SDL SimUI Command File Command List-Ready-Queue Command Entry PId State Signals Signal BtoA:1 start state dispatch: 1 start state <<Block DLCa>> dispatch: 1 start state <<Block DLCb>> List-Process - Command Figure 4.7 The Simulator Command Window MSC SimulatorTrace MSC SimulatorTrace env_0 DLCaSU DLCbSU Figure 4.8 Environment: default (a) and Define-MSC-Trace-Channels (b) C. In the Select window, select 0 /* Basic MSC */ and press OK : the MSC Editor displays the MSC trace. D. Arrange the Simulator and SDL and MSC Editors windows as in Figure 4.9. 4.2.2 Validate against the 