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4. MEWTOCOL
4.1 Communication Procedure
Communication starts with command transmission from the host computer, and ends with the response
of the KT4R (controller).
4.1.1 Response with Data
Host computer
4.1.2 Acknowledgement
Host computer
Acknowledgement
4.1.3 Negative Acknowledgement
Host computer
Non-existent command or
data out of the setting range
Negative acknowledgement
4.2 Communication Timing of the RS-485
Master side (Take note while programming)
When the master starts transmission through the RS-485 communication line, the master is arranged so
as to provide an idle status (mark status) transmission period of 1 character or more before sending the
command to ensure synchronization on the receiving side.
Set the program so that the master can disconnect the transmitter from the communication line within a
1 character transmission period after sending the command in preparation for reception of the response
from the slave.
To avoid collision of transmissions between the master and the slave, send the next command after
carefully checking that the master has received the response.
If a response to the command is not returned due to communication errors, set the Retry Processing to
send the command again. (It is recommended to execute Retry twice or more.)
Slave side
When the slave starts transmission through the RS-485 communication line, the slave is arranged so as
to provide an idle status (mark status) transmission period of 1 ms or more
to ensure synchronization on the receiving side.
The slave is arranged so as to disconnect the transmitter from the communication line within a 1 character
transmission period, after sending the response.
(*) Can be set in [Response delay time (p.5.)] within a range of 0 to 1000 ms.
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KT4R
Read command
Response data
(Fig. 4.1.1-1)
KT4R
Write command
(Fig. 4.1.2-1)
KT4R
(Fig. 4.1.3-1)
When the host computer sends the Read command,
the KT4R responds with the corresponding set value
or current status.
When the host computer sends the Write command,
the KT4R responds by sending acknowledgement
after processing is terminated.
When the host computer sends a non-existent
command or value out of the setting range, the KT4R
returns a negative acknowledgement.
before sending a response
(*)
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