Message types

ASIM team
LIP6 Laboratory
Paris, France

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PCI-DDC offers three kind of messages : standard, short and composed messages.

standard message:: There is one transmitter and one receiver. A standard message may be any length and consists of one to several pages described in the LPE. The receiving PCI-DDC component may use the LRM to count the received packets and the LMI to write the report. Messages are not necessarily word-aligned.
Short message:: A short message contains 8 bytes of data. Data are fetched directly in the LPE and written directly in the LMI. The protocol is simpler since several PCI bus transactions are saved (i.e. 4, 5 and 6).
Composed message:: There are several transmitters and one receiver. The receiver detects the message completion when each transmitter have sent one message. This kind of message does not transfer any data. It is used to realize synchronization barriers. All piece of a composed message must have the same Message Identifier (MI). The receiving PCI-DDC's LRM is used for giving the expected transmitter number.

Next: Internal architecture Up: Functional Description Previous: The ``remote write'' primitive