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MELSEC-Q
7 COMMUNICATION WITH EXTERNAL DEVICES
• Stop bit • • • Specify this parameter when using the ZOPEN instruction.
Specify the data delimiter. The following values can be set in BASIC:
• 1 bit • • • The data delimiter is represented by 1 bit.
• 2 bits • • • The data delimiter is represented by 2 bit.
• 1.5 bits • • • The data delimiter is represented by 1.5 bit.
Specify the following items as necessary.
Details of the DC1/DC3 control and signal control are explained in Appendix 6.
• Size of the receive buffer • • • Specify this parameter when using the ZCNTL
instruction.
The receive buffer is a memory area where the received data is automatically stored
even if the data receive instruction is not executed when the data is received from
the external device.
All the data received while the data receive instruction is not executed will be ignored
if 0 is specified as the receive buffer size.
• DC1/DC3 control • • • Specify this parameter when using the ZCNTL instruction.
If the DC1/DC3 control is activated on the communication module, a DC3 code is
sent when the receive buffer becomes full and a DC1 code is sent when the buffer
space becomes available while receiving data.
During the data transmission, the transmission is stopped when a DC3 code is
received, and it is resumed when a DC1 code is received.
The settings of the DC1/DC3 control on the communication module side and on the
external device side have to be the same.
• Signal control specification • • • Specify this parameter when using the ZCNTL
instruction.
Transmission and reception of data are controlled by the CS (CTS), RS (RTS) (RS-
232C/RS-422), ER (DTR), and DR (DSR) (RS-232C only) signals of the interface.
The following table shows what occurs when each control signal is activated or
deactivated.
Signal
Control activated
Control deactivated
CS (CTS)
Input signal.
The data is sent when this signal is ON.
This control cannot be
deactivated for the RS-232C
interface.
RS (RTS)
Output signal.
This signal is turned ON when the data
can be received normally.
The data is received regardless of
the signal.
DR (DSR)
Input signal.
The data is sent when this signal is ON.
The data is sent regardless of the
signal.
• The CS (CTS)
control signal is
always active for the
RS-232C interface.
• There are no DR
(DSR) and ER (DTR)
control signals for the
RS-422 interface.
ER (DTR)
Output signal.
This signal is turned ON when the data
can be received normally.
The data is received regardless of
the signal.
The settings of the control signal specifications do not need to be the same on the
communication module side and on the external device side. They change depending
on the signal connections of the cable, however, so care must be taken.
