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MELSEC-Q
4 FUNCTIONS
(4) Overview of each connection type
One of the connection types shown below can be selected for each slave node.
For available connection types, refer to the manual for each slave node.
• Polling
• Bit strobe
• Change of state
• Cyclic
I/O communications of respective connection types are explained below.
(a) Polling
Polling is a communication method by which the following steps 1) to 6) are
repeated to slave nodes.
1) The master node sends output data.
2) Step 1) triggers input data transmission from the slave node.
3) The master node sends output data.
4) Step 3) triggers input data transmission from the slave node.
5) The master node sends output data.
6) Step 5) triggers input data transmission from the slave node.
Master node
1)
2)
Slave node
3)
4)
5)
6)
Summary of Contents for QJ71DN91
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