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APPENDIX
1 When the communication module is started up, the ER (DTR) control signal is turned OFF.
The ER (DTR) control signal turns ON when the communication channel is opened. After that, the ER
(DTR) 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 ER (DTR) 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 ER (DTR) control signal does not turn OFF even if the communication channel is closed.
Even after the channel is closed, the ER (DTR) 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 - 29
• In order to enable the ER (DTR) control, specify 1 or greater in the receive buffer specification when
opening the communication channel.
• The ER (DTR) control signal is turned OFF if the communication channel is opened without enabling
the ER (DTR) control.
• The RS (RTS) control has the same control function as the ER (DTR) control.
Determine which of the control functions of the communication module to use depending on
the external device's specifications.
MELSEC-Q
App - 29
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