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6.6 Things to be Noted during RTU Communication
6.6.1 Timing of Transmission
Upon using RS-485, set enough response delay time to ensure the communication (sending/receiving) with
the host computer.
See Figure of "6.1 Communication Procedures" and "5.8 Setting of Response Delay Time."
6.6.2 Request Interval
If the "request message" is to be sent continuously by the upper computer, wait for at least 2msecs. from
the arrival of the "response message" from this product before sending the next request message.
6.6.3 Conditions for Response
This product will not return the "response message" if there is a time interval of more than 3.5 characters
between data that consist the "request message" since it cannot identify these data as one whole "request
message."
Therefore, although there is an error in the "request message," the "response message" with ERR will not
be returned unless the above condition is met.
Therefore, the upper computer should resend the necessary "request message" if the "response message" is
not returned within the reasonable time.
At a time interval of more than 3.5 characters, this product clears all characters that were received prior
to the said interval.
6.6.4 Address Specification Error
This product will not respond to any "request message" that specifies the address that is other than the
one that has been set to itself.
Therefore, if there is an error in the address section of the "request message," none of the slave stations
will return the "response message."
Therefore, the upper computer should resend the necessary "request message" if the "response message" is
not returned within the reasonable time.
6.6.5 Number of Digits of Data and Position of Decimal Point
See "6.5 Explanation about Codes (g) Numerical Data."
6.6.6 Operation After the Receiving of Save Request Message
This product starts the saving of data once it receives the save request message correctly from the upper
computer.
Only the data that is different from the one stored in the EEPROM (changed data) shall be saved.
Time that is required to save the data (TW) is within 6 seconds.
The product sends a message when the saving of data is completed.
Some data may be lost if the product is turned OFF while the saving process is in progress. Do not turn
the power of this product OFF for at least 6 seconds after the sending of save request message.
6.6.7 Upon Turning the Power ON
This product will not perform any communication for approximately 4 seconds after turning its power ON
(no response). Set the delay from power ON to start communication.
6.6.8 Saving the Data Other than Save Request Message
This product saves the parameter into the EEPROM even without receiving the save request message in case
of the following:
1) If the parameter is changed through key operation, it writes only changed parameters and
other related parameters.
2) If the auto tuning is activated and ended normally, only the PID constant will be written.
6.6.9 Change of Setting (alue (S( or S(2) by the Communication during Auto Tuning
If the value for control (S( or S(2) is changed via communication while the auto tuning is performed,
the said value (S( or S(2) will not be changed until auto tuning ends.
