Figure 5-17 Data Synchronicity Assurance - Hitachi FL.NET User Manual

(4) Data synchronicity assurance
In cyclic transmission, the data to be transmitted is divided into frames depending its size.
The following procedures are used to assure common memory (internal memory such as the
FL.NET module) synchronicity on an individual node basis.
Transmission timing
When a data transmission is requested by a higher layer, the cyclic data of the self-node is
copied to a buffer to prepare for transmission and then sequentially transmitted. If the
size of the data retained by a transmitting node is larger than the maximum permissible
size limit for the transmission of one frame, the buffered data is divided into two or more
frames for transmission.
Reception sequence refresh timing
When a receiving node completely receives cyclic data from another node, it refreshes the
associated area while maintaining the synchronicity with a higher layer.
Even when cyclic data is transmitted after being divided into two or more frames, the
associated area refreshes when all the frames sent from a node are completely received.
If all such transmitted frames are not received, the entire data received from the
transmitting node is discarded.
Transmitting end
On network
circuit
Receiving end
Common memory
Common memory
Cyclic data

Figure 5-17 Data Synchronicity Assurance

Transmission
area
Collective copying
Send buffer
Cyclic data
Cyclic data
Receive buffer
Reception
area
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5 USER GUIDE
Collective copying