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13. COMMUNICATION FUNCTIONS
13.7 Time-out operation
The master station transmits EOT when the slave station does not start reply operation (STX is not
received) 300[ms] after the master station has ended communication operation. 100[ms] after that, the
master station retransmits the message. Time-out occurs if the slave station does not answer after the
master station has performed the above operation three times. (Communication error)
E
O
T
300ms
100ms
E
O
T
300ms
100ms
E
O
T
300ms
100ms
300ms
Message
Message
Message
Message
*Time-out
Master station
Slave station
13.8 Retry operation
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 operation). A
communication error occurs if the above operation is repeated and results in the error three or more
consecutive times.
Message
Message
Message
*Communication error
Master station
Slave station
S
T
X
S
T
X
S
T
X
Station number Station number Station number
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 operation is performed three times.