User`s manual

204
7.1 Control Contents of DTR/DSR (ER/DR) Signal Control
This control uses the RS-232 interface DTR/DSR signals to inform the external device whether or not the local station
is ready to receive data.
The Q series C24 uses the ER (DTR) signal to inform the external device whether or not the local station is ready to
receive data and uses the DR (DSR) signal to check if the external device is ready to receive data.
(1) Q series C24 DTR control
(a) Q series C24 DTR control
The Q series C24 uses the ER (DTR) signal to inform the external device whether or not it is ready to receive
data.
The data transmitted from the external device by non procedure protocol is stored to the buffer memory receive
data storage area through the OS area. ( User's manual (Basic))
For the following conditions, the receive data is temporarily stored to the OS area and is transferred to the
receive data storage area when the present receive data read processing is complete.
• Receive data size exceeds the size of the buffer memory area when "receive data storage area < receive
data length data" was received.
• The data was received before the sequence program read the previously received data.
The Q series C24 turns the ER (DTR) signal on/off as listed below, depending on the size of the vacant OS
area.
• Vacant area 64 bytes (default) or less: Off
• Vacant area 263 bytes (default) or more: On
External device
Programmable
controller CPU
ER(DTR) signal
DR(DSR) signal
Data 1-1
Data 1-2
Data 1-2 Data 2-2
(Terminate)
(Restart)...Continue
(Terminate)
(Restart)...Continue
ON
OFF
ON
OFF
ER(DTR) signal
Vacant area
(Data storage)
8448
bytes
64 bytes
or less
(default)
Vacant area
(Data storage)
8448
bytes
263 bytes
or more
(default)
Receive preparations
complete
ON: Ready to receive
OFF: Not ready to receive
After read complete from
sequence program
Q series C24
(OS area)
Q series C24
(OS area)