Mitsubishi MELSEC L Series User Manual page 194

(2) Q series C24 DSR control
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(b) Specification of free OS area
The limit of free OS area for data reception under the DTR/DSR (ER/DR)
signal control is specified in GX Configurator-SC's "Transmission control
and others system setting".
When it reaches the limit, this status is notified to disable data reception.
The set values must satisfy the following condition.
"Transmission control start free area < Transmission control end free area"
1) Transmission control start free area specification (Address:
2012 /2112
H
Specifies an available capacity in the OS area so that the full status is
notified to disable the data reception (ER (DTR) signal is OFF).
• Transmission control start free area: 64 to 4095 (Default: 64)
2) Transmission control end free area specification (Address:
2013 /2113
H
Specifies an available capacity in the OS area so that data reception is
enabled by notification (ER (DTR) signal is ON).
• Transmission control end free area: 263 to 4096 (Default: 263)
REMARKS
• "Receive data clear" described in User's Manual (Basic) clears the data stored in
the OS area. (The receive area in the buffer memory is not cleared.)
• If more data is received when the OS area mentioned above are 0 bytes, an SIO
error is generated and the data received until the OS area becomes vacant is
ignored. At this time, the SIO signal is turned on. (Refer to the User's Manual
(Basic).)
The Q series C24 uses the DSR signal to detect whether or not the external
device is ready to receive data and to control data transmission to the external
device as shown below, depending on whether the DSR is on/off.
1) If the DSR signal is ON and there is send data, the Q series C24 transmits it
to the external device.
2) If the DSR signal is OFF, even if there is send data, the Q series C24 does
not transmit it to the external device.
When the DSR signal is turned on, the Q series C24 transmits the send data
to the external device.
7 DATA COMMUNICATIONS USING DC CODE TRANSMISSION CONTROL
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H
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H
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