7-20
Outline of operation when using computer link (MEWTOCOL slave)
Command and response
• Instructions issued by the computer to the PLC are called commands. Messages sent back to the
computer from the PLC are called responses. When the PLC receives a command, it processes the
command regardless of the sequence program, and sends a response back to the computer.
MEWTOCOL-COM sketch
• Communication is carried out in a conversational format, based on the MEWTOCOL-COM
communication procedures.
• Data is sent in ASCII format.
• The computer has the first right of transmission. The right of transmission shifts back and forth
between the computer and the PLC each time a message is sent.
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