Principle

ASIM team
LIP6 Laboratory
Paris, France

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From the hardware point of view, a message transmission procedure consists of three stages: preparation, transmission and reception.

Preparation
Page Descriptors of the message are pushed by software into the LPE. (See page for more details). Then, the software informs the PCI-DDC component of the added page number by writing in a PCI-DDC configuration register. Software must lock those pages during the transmission.
Transmission
PCI-DDC, at the sender side, asks for the PCI-bus and reads the LPE using DMA accesses in master mode. Then, it performs data transmission, using DMA accesses. There is no overhead for the processor during the transmission. The physical remote address is transmitted with every packet. When the last page is sent, PCI-DDC can notify the sending processor with an interrupt signal (this can be defined on a message base).
Reception
At the receiver side, as soon as PCI-DDC begins to receive packets, it asks for the PCI-bus and writes data at the specified address into the main memory using DMA accesses in master mode. There is no overhead for the processor during the reception. When the last page is written, PCI-DDC can notify the processor, either with an interrupt signal, and/or by writing in the LMI.

Next: Message types Up: The remote write primitive Previous: The remote write primitive