 V76 model. */ DLCaSU DLCbSU (su2dlc) (su2dlc) DLCa : V76_DLC DLCb : V76_DLC V76frame V76frame DLCaDL DLCbDL V76frame V76frame dataLink Figure 4.34 The V.76 model waits for external signals process dispatch(1, 1) ready L __DataReq L_ReleaseRec L_EstabReg (DLCnum, uData) (DLCnum) (DLCnum) Figure 4.35 Some of the external signals required in the blocks DLCa and DLCb Interactive Simulation 73 Filter Filter Channel List: Signal List: dicasu _datareq(dicident.integer) dlcbsu estabreq(dicident) estabresp _releasereq(dicident) Filter Process List: dicaldispatch Channel: dlcasu Signal: _estabreq(0) [TO]: Feed List: Delete DeleteAll Close Figure 4.36 Adding feed commands A. In the Simulator, select Edit > Feed: the window shown in Figure 4.36 appears. Select a channel (1), a signal (2), enter the value of the parameter(s) (3) and press on Add: you have created one feed. This means that every time the process dispatch in the block DLCa is in a state where the input of L_EstabReq is possible (i.e. input queue empty and state = ready, see Figure 4.35), the Simulator will propose to execute the input of L_EstabReq by dispatch²8. B. Continue in the same way to create the following feed list, then press on Close. dlcasu l_estabreq (0) dlcasu l'estabreq (1) dlcasu l_setparmreq ( ) dlcasu l_releasereq (1) dlcasu l_datareq (0, 86) dlcasu 1_datareq (1, 39) dlcbsu l_estabresp 28 As opposed to actual signal outputs, signals sent by Simulator feed commands do NOT go into the input queue of the target process (here dispatch). The behavior is equivalent, but not using the queue reduces the number of global states during exhaustive simulation. 74 Validation of Communications Systems with SDL dlcbsu l setparmresp ( ) dlcbsu l releasereg(0) C. The feed commands created here will be necessary for all the exercises in the book. To avoid entering them manually repeatedly, save them: in the Simulator window, type as shown in Figure 4.37, terminated by return: list feed >> v76_feed.wri Now: 0 list feed >> v76 feed.wri Figure 4.37 Saving the fee