Changes between Version 7 and Version 8 of TLMDT

Timestamp:

May 13, 2011, 3:35:05 PM (14 years ago)

Author:

gioja

Comment:

--

TLMDT

@@ -149 +149 @@
 
 === 2.3. PDES Null_response
-The Null_response is a message which transits on networks like a VCI responses. Only transactions which are blocking or conditionnaly blocking needs to receive Null_responses. The meaning of this message is : "The response to the associated VCI transaction won't be caught before this time". The Null_response is part of the Active_Sync mechanisms. It is used to predict the future of simulation. The only useful data contained in the Null_response is the temporal information. When an initiator receives a Null_response instead of a VCI response, it allows itself to pursue its treatment, neglecting the need of the VCI response, until the Null_response time. In order to properly aim the right transaction on the right initiator, the VCI transaction is reused for the Null_response. When the Null_response is sent, only the target of this message is awaken. Multiple Null_responses can be sent for a single VCI transaction. Successives Null_response's time related to the same transaction needs to grow.
+The Null_response is a message which transits on networks like a VCI responses. Only transactions which are blocking or conditionnaly blocking needs to receive Null_responses. The meaning of this message is : "The response to the associated VCI transaction won't be caught before this time". The Null_response is part of the Passive/Active_Sync mechanisms. It is used to predict the future of simulation. The only useful data contained in the Null_response is the temporal information. When an initiator receives a Null_response instead of a VCI response, it allows itself to pursue its treatment, neglecting the need of the VCI response, until the Null_response time. In order to properly aim the right transaction on the right initiator, the VCI transaction is reused for the Null_response. When the Null_response is sent, only the target of this message is awaken. Multiple Null_responses can be sent for a single VCI transaction. Successives Null_response's time related to the same transaction needs to grow.
 
 Interconnects and targets can generate and transmit the Null_responses. Null_responses are useful for preventing deadlocks related to synchronization. For performance optimizations, an interconnect can neglect generating a Null_response when the associated transaction is primary. Since Null_response allows to release parallelism of the simulation, it seems important to send it with the highest time possible.
@@ -204 +204 @@
 
 === 2.5. Passive_Sync / Active_Sync
-
+According to the TLMDT for SOCLIB specification, an initiator which sends a blocking request will be completely locked until the response comes back. However, targets are not ever only reactive and won't ever immediately answer to a request, possibly waiting another request which could be handled before the first one, due to the target structure. In this case, if the initiator doesn't transmit a greater time information than the one of its last request, the related interconnect won't be able to route any other request to the waiting target. The null_response is the message which allows to inform an initiator that it needs to increase its own time up to the one in the message.
+
+There are two methods for handling the null_responses.
+The first and easiest one is to continue to consider that an initiator is fully locked until the real response is caught. This way, the only thing to do when a null_response is caught is to send a null_command to the interconnect with the same time information as the null_message. This doesn't even need to wake up the initiator. 
 == 3. Efficient time modeling in a multi-transactionnal VCI Component
 == 4. VCI Initiator modeling