404
8 COMMUNICATION FUNCTION (MITSUBISHI ELECTRIC AC SERVO PROTOCOL) [A]
8.3 Protocol
Time-out processing
The master station transmits EOT when the slave station does not start a return processing (STX is not received) in 300 ms
after the master station ended communication processing. Then, the master station retransmits the message in 100 ms. Time-
out occurs if the slave station does not answer after the master station has performed the above communication processing
three times. (communication error)
Retry processing
When a fault occurs in communication between the master and slave stations, the error code in the response data from the
slave station is a negative response code ([B] to [F], [b] to [f]). In this case, the master station retransmits the message which
was sent at the occurrence of the fault (retry processing). A communication error occurs if the above processing is repeated
and results in the error three or more consecutive times.
Similarly, when the master station detects a fault (e.g. checksum, parity) in the response data from the slave station, the
master station retransmits the message which was sent at the occurrence of the fault. A communication error occurs if the
retry processing is performed three times.
Initialization
After the slave station is switched on, it cannot return to communication until the internal initialization processing terminates.
Therefore, at power-on, start ordinary communication after doing the following:
• Wait for 3.5 s or longer after the slave station is switched on.
• Check that normal communication can be made by reading servo parameters or other data which does not pose any safety
problems.
300 ms
100 ms
300 ms
100 ms
300 ms
100 ms
300 ms
Message
Controller side
(master station)
Servo side
(slave station)
Message
Message
Message
*Time-out
EOT
EOT
EOT
STX
Message
Message
*Communication error
Message
Station No.
Station No.
Station No.
Controller side
(master station)
Servo side
(slave station)
STX
STX