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BUFFER
7. FIXED
EXCHANGE WITHOUT PROCEDURE
7.3.3
MELSEC-A
Precautions When Using Simultaneous Broadcast Communications
Functions
Following are precautions when conducting simultaneous broadcast communicationwith fixed buffer
exchange without procedures.
For simultaneous broadcast communication, theuser will arrange the simultaneous
broadcast transmissiodreception special port
No. and specify the portNo. for it.
The simultaneous broadcast communication
transmission message is set to all the nodes
on the Ethernet to which the
E71 is connected.
All of the nodes connected to the same
Ethernet determine whetherthe receivedrnessage broadcast by simultaneous broadcast communication is necessary, and when
unnecessary, must conduct readand discard processing.
* When the transmitted message is unrelated to a particular node, the particular node will
discard the received message. Inaddition, even if a particular node is the subject station,do
not return a response. The E71 will automatically perform this processing.
14h
The application data amount that can
be handled at onetime for transmission or reception is a maximum
of 2046 bytes. If data of 2047 bytes or more must be transmitted or
received, divide it at the transmissionorigin.
When the reception data is read to the PLC CPU when the reception end signal ( X O ,
X2...XE) is turnedon, be sure to turn on the corresponding reception end check
signal
(Yo to Y7).
Turning on the reception end check signal
(YO to Y7) makes it possible for theE71 to
store the received data in the subject
fixed buffer.
Not turning on
the reception end check
signal ( Y O to Y7) could cause the reception data
to be discarded.
During the period between when the reception end signal turns onto when the reception end check
signal is turned on, the data to be received (including the header) is stored in the E71's OS internal
buffer.
The OS internal buffer capacity is approximately 43k bytes. The portion of the reception data that
exceeds this capacity will be discarded.
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