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6 - 13
MELSEC-F
FIXED BUFFER COMMUNICATION (WITH THE PROCEDURE EXIST
CONTROL METHOD)
6
6 - 13
6.5 Programming
This section explains the programming method when the Ethernet module
communicates with an external device using fixed buffers and the procedure exist
control method.
6.5.1 Precautions when creating programs
(1) In order to communicate using the fixed buffer, the initial processing and the
connection open processing must be completed.
(2) The contents of the parameter settings have been loaded into the Ethernet
module when the Ethernet module open completion signal (BFM#20480
corresponding bit) switches from off to on.
(3) The data length (word count) is established using the instruction for procedure
exist communication control method.
If the send data length exceeds this range at data sending, a communication
error occurs and the data is not sent.
(4) Reading or writing to the buffer memory using fixed buffer communication.
• Data sending
Write the send data in the buffer memory (BFM#1664 to #9855).
Write "0001
H" in BFM#1610 to #1617 to send the data.
• Data receiving
Check the data received (BFM#1610 to #1617: "0001
H") and read the received
data to the PLC (BFM#1664 to #9855).
After reading out, write "0002
H" in BFM#1610 to #1617 to send the response.
(5) The following should be observed when using a connection opened by UDP.
External devices can be switched by modifying the setting values in the
communication address setting area of the communication parameter setting
area before sending/receiving data. Thus, data can be sent to multiple external
devices sequentially. When sending/receiving, make sure to switch between
external devices properly so that no communication problems occur.
(6) For data (command) transmission, the next data (command) should be after the
data communication is complete (such as after receiving a response) for the
transmission of the previous data (command).