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7 COMMUNICATION WITH EXTERNAL DEVICES
7.3.4 Communication with other external devices
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The following explains how to communicate with external devices, other than terminals
and printers, which are connected either to the RS-232C or the RS-422/RS-485
interface of the communication module, as well as precautions when carrying out the
communication.
(1) To transmit data • • • Use the ZSEND instruction.
1) Open the interface and specify the communication parameters according
to the external device to be used.
ZOPEN # <channel number>, <control table>
ZCNTL # <channel number>, 0, <control table>
2) Prepare the data to transmit, then specify the number of bytes of transmission data an
the timeout in the control table used for the ZSEND instruction.
3) Execute the ZSEND instruction.
ZSEND # <channel number>, <control table>, <output element>
When the execution of the ZSEND instruction is completed, the number of bytes
of transmitted data is stored in the control table used for the ZSEND instruction.
A
D51H
4) An error occurs if the data was not sent normally. In this case, check the condition
of the communication line, the communication parameters of the interface,
the contents of the control table, etc.
• There are many potential reasons why the communication
cannot be performed correctly.
They could be cables, connectors, parameters, etc • • •.
Please check each possible cause one by one even though
it's time consuming.
• When the ZSEND instruction is used, the Kanji code conversion
using the ZCNTL and KMODE instructions cannot be performed.
REMARK
• Timeout • • • Specifies the time (in seconds) that is allowed to pass from the start
of the communication before a timeout error occurs if the
communication for some reason did not finish.
ZSEND
MELSEC-Q
"ABCD • • • • • • "
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