Changes between Version 5 and Version 6 of Writing Rules/Tlmt

Timestamp:

Dec 25, 2007, 12:16:29 AM (18 years ago)

Author:

alain

Comment:

--

Writing Rules/Tlmt

@@ -58 +58 @@
 and VCI_CMD_STORECONDITIONAL  Le champ address contient un ensemble d’adresses valides dans l’espace mémoire partagé du système modélisé. The contig field can be used for optimisation.
 
-The '''cmdSend()''' function is non-blocking. To implement a blocking transaction (such as a cache line read, where the processor is blocked during the VCI transaction), the model designer must use the '''wait()''' method, that is a member function of the '''VciInitiatorPort''' class. The '''execLoop()''' thread is suspended; It will be activated when the response packet is received by the '''notify()''' method, that is also a member function of the '''VciInitiatorPort'''.
+The '''cmdSend()''' function is non-blocking. To implement a blocking transaction (such as a cache line read, where the processor is ''frozen'' during the VCI transaction), the model designer must use the '''wait()''' method, that is a member function of the '''VciInitiatorPort''' class. The '''execLoop()''' thread is suspended. It will be activated when the response packet is received by the '''notify()''' method, that is also a member function of the '''VciInitiatorPort'''.
 
 == C.2) Receiving a VCI response packet ==
 
+To receive a VCI response packet, a call-back function must be defined as a member function of the class '''my_initiator'''. This call-back function (named '''rspReceived()''' in the example), will be executed each time a VCI response packet is received on the '''p_vci''' port. The function name is not constrained, but the arguments must respect the following prototype:
+{{{
+void  rspReceived(vci_rsp_t  *rsp,
+               sc_time  time)
+}}} 
+The informations transported by a VCI command packet are defined below:
+{{{
+class vci_rsp_t {
+vci_command_t  cmd;  // VCI transaction type
+uint32_t  length;  // number of words in the packet
+bool  eop;  // end of packet marker
+uint32_t  srcid;  // SRCID VCI
+uint32_t  trdid;  // TRDID VCI
+uint32_t  pktid;  // PKTID VCI
+}
+}}}
+The actions executed by the call-back function depend on the transaction type ('''cmd'''  field), as well as the '''pktid''' and '''trdid''' fields. In the proposed example :
+ * In case of of a blocking read , the call-back function updates the local time, and activates the suspended threadwith the by the '''notify()''' method.
+ * In case of a non-blocking write, the call-back function does nothing.
+ 
 == C.3) Initiator Constructor ==
 
+The constructor of the class'''my_initiator''' must initialize all the member variables, including the VCI port. The '''rspReceived()''' call-back function being executed in the context of the thread sending the response packet, a link between the '''p_vci''' port and the call-back function must be established. Moreover, the '''p_vci''' port must contain a pointer on the initiator local time.
+The VciInitiatorPort constructor must be called with the following arguments:
+{{{
+p_vci(“vci”, this, &my_initiator::rspReceived, &m_time);
+}}}
+  
 == C.4) Lookahead parameter ==
 
-== C.5) TLM-T initiator example ==
+The SystemC simulation engine behaves as a cooperative, non-preemptive multi-tasks system. Any thread in the system must stop execution after a given time, in order to allow the other threds to execute. With the proposed approach, a TLM-T initiator will never stop if it does not execute blocking communication (such as a processor that has all code and data in the L1 caches). This can block the simulation.
+
+To solve this problem, it is necessary to define - for each initiator module- a '''lookahead''' parameter. This parameter defines the maximum number of cycles that can be executed by the thread before it stops. The '''lookahead''' parameter allows the system designer to bound the de-synchronization between threads. 
+A small value for this parameter result in a better timing accuracy for the simulation, but implies a larger number of context switch, and a slower simulation speed. 
+
+== C.4) TLM-T initiator example ==
 
 {{{