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3. Instructions
CS/CJ/NSJ Series Instructions Reference Manual (W474)
Serial Communications Instructions
3
TXD
Flags
Related Auxiliary Area Words and Bits
z RS-232C incorporated in the CPU Unit
z Port 1 of Serial Communications Board (Unit Version 1.2 or Later)
z Port 2
Related PLC Setup Settings for the CPU Unit's Built-in RS-232C Port
z CX Programmer settings
Name Label Operation
Error Flag ER • ON if the CPU Unit's RS-232C port is specified as the send port, but no-protocol mode is not set in
the PLC Setup.
• ON if one of the Serial Communication Board's serial ports is specified as the send port, but no-pro-
tocol mode is not set in the port's allocated DM Setup Area.
• ON if the value of C is not within range.
• ON if the value for N is not between 0000 and 0100 hex.
• ON if a send is attempted when the Send Ready Flag is OFF. (The Send Ready Flag is A39205 for
the CPU Unit's RS-232C port, A35605 for Serial Communications Board port 1, or A35613 for Serial
Communications Board port 2.)
• ON (ER Flag in interrupt tasks) if a TXD(236) or RXD(235) instruction is being executed for the Serial
Communications Board in the cyclic task, the cyclic task is interrupted, and another TXD(236) or
RXD(235) instruction is executed for the Serial Communications Board in the interrupt task.
• ON if a TXD(236) was executed for a serial port on a Serial Communications Board that was being
restarted.
• OFF in all other cases.
Port Address Contents
CPU Bus Unit's built-in RS-232C Port A392.05 ON when data can be sent in the no-protocol mode.
Port Address Contents
Serial Communications Board port 1 A356.05 ON when data can be sent in the no-protocol mode.
Port Address Contents
Serial Communications Board port 2 A356.13 ON when data can be sent in the no-protocol mode.
Name Address Contents
Ports 1 and 2 Inner Board Service
Disabled Flag
A424.04 ON when TXD(236) is executed for a Serial Communications Board that
does not support no-protocol mode (a Board without a version number).
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