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Chapter 7: Computer Link Function
7
(4) Guarantee of simultaneity
The cyclic transfer divides data into frames, depending on the amount of data being sent.
The FL-net guarantees the simultaneity on common memory of each node using the following proce-
dures.
Note: When area 2 exceeds 3084 bytes, the JW-50FL cannot guarantee the simultaneity
of the data for hardware reasons.
1 Data transmission timing
When a node receives a request to send data from the upper layer, it copies its own cyclic data
into a buffer and sends the data, one word after another. When the amount of data being sent is
more than will fit in one frame, it divides the data in the buffer into multiple frames before
sending.
2 Refresh timing when receiving
After a node has received all the cyclic data from some other node, it will refresh the correspond-
ing area while synchronizing with the upper layer.
When a cyclic data is sent as multiple frames, the receiving node will refresh the area after receiv-
ing all the frames from the other node. If any of the frames is missing, it will delete all the data from
that node.
Guarantee of simultaneity of data
Common memory
Data receiving side
On network
circuit
Group copy
Data sending side
Data sending buffer
Data receiving buffer
Cyclic data
Common memory
Sending
area
Cyclic data
Cyclic data
Data receive
area
Group copy