973
Serial Communications Instructions Section 3-24
Instructions Communications frames Function
TXD(236),
RXD(235),
TXDU(256),
and
RXDU(255)
Sends or receives data in one direction only.
A send delay can be set.
PMCR(260) Up to 16 steps can be defined for sending
and receiving.
Steps can be changed and retry processing
performed based on responses.
Communications monitoring times can be
set.
Symbols can be read/written for the PLC.
Repeat symbols can be used.
Other.
Instructions Mode Communications ports
TXD(236)
and
RXD(235)
No-protocol
(custom)
TXDU(256)
and
RXDU(255)
No-protocol
(custom)
PMCR(260) Protocol macro
Data Data
Data Data
Only End Code
Data Data
Any of the following can be used.
No Start or End Code
Start and End Code
Only Start Code CR+LF End Code
Start and CR+LF End Code
Header Address
The following type of frames (messages) can be created
to meet the requirements of the external device.
Data
Error check
Terminator
Communications steps
can be created.
I/O memory
Read/write
TXD(236)/
RXD(235)
RXD(235)
TXD(236)
TXD(236) and RXD(235)
use serial ports on the
CPU Unit or Serial
Communications Boards
(Ver. 1.2 or later).
Serial port in CPU Unit or Serial Communications Board
CPU Unit
TXDU/RXDU
RXD
TXD
Serial Port of Serial Communications Unit (Version 1.2 or later)
CPU Unit
Serial Communications unit
Serial Commu-
nications Board
Serial Communications Board (CS Series
only)
Receive
Send
Send
Receive
Serial Communications Unit
Serial Communications Unit
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