Serial Communications Instructions - Omron CJ - INSTRUCTIONS REFERENCE MANUAL 07-2009 Reference Manual

3. Instructions
Serial Communications
Instructions

Serial Communications Instructions

There are two types of serial communications instruction. The TXD(236), RXD(235), TXDU(256), and
RXDU(255) instructions send and receive data in no-protocol (custom) communications with an
external device. PMCR(260)/PMCR2(264) sends and receives data using user-defined protocols with
an external device. The difference is shown in the following tables.
Note • The TXD(236) and RXD(235) instructions transfer data only through the CPU Unit's built-in serial port or
a serial port on a Serial Communications Board (Ver. 1.2 or later).
• The TXDU(256) and RXDU(255) instructions transfer data only through a Serial Communications Unit
(Ver. 1.2 or later).
• PMCR(260) and PMCR2(264) can be used only for the serial ports on Serial Communications
Units/Boards.
Instructions
TXD(236), Any of the following can be used.
RXD(235),
No Start or End Code
TXDU(256),
Data
and
RXDU(255)
Only Start Code
Only End Code
Data
PMCR(260) The following type of frames (messages) can be created to meet the
and requirements of the external device.
PMCR2(264)
Header Address
Communications steps
can be created.
812
Communications frames
Start and End Code
Data
CR+LF End Code
Data Data
Start and CR+LF End Code
Data
Data
Error check Terminator
I/O memory
Read/write
Function
Sends or receives data in one direction only.
A send delay can be set.
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.
CS/CJ/NSJ Series Instructions Reference Manual (W474)