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APPENDIX
1 When the communication module is started up, the RS (RTS) control signal is turned OFF.
The RS (RTS) control signal turns ON when the communication channel is opened. After that, the RS
(RTS) control signal turns ON and OFF when data is received depending on the size of the free area in
the receive buffer.
2 Even if the RS (RTS) control signal is turned OFF, the received data is stored in the receive buffer until
there is no more free area in the receive buffer.
3 The RS (RTS) control signal does not turn OFF even if the communication channel is closed.
Even after the channel is closed, the RS (RTS) control continues and data received from the external
device is stored until there is no more free area in the receive buffer. However, the received data
remaining in the receive buffer when the communication channel is closed and the received data stored in
the receive buffer after the communication channel is closed cannot be read by the BASIC program. When
the communication channel is reopened, the received data in the receive buffer is cleared.
App - 31
• In order to enable the RS (RTS) control, specify 1 or greater in the receive buffer specification when
opening the communication channel.
• The RS (RTS) control signal is turned OFF if the communication channel is opened without enabling
the RS (RTS) control.
• The ER (DTR) control has the same control function as the RS (RTS) control.
Determine which of the control functions of the communication module to use depending
on the external device's specifications.
MELSEC-Q
App - 31
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