Serial Communications Instructions - Omron CJ - REFERENCE MANUAL 10-2009 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),
RXDU(255), DTXDU(262), and DRXDU(261) 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 • TXD(236) and RXD(235) are used for built-in CPU Unit serial ports and serial ports on Serial Communi-
cations Boards with unit version 1.2 or later.
• TXDU(256) and RXDU(255) are used for serial ports on Serial Communications Units with unit version
1.2 or later.
• DTXDU(262) and DRXDU(261) are used for serial ports on CJ1W-SCU22/SCU32/SCU42 Serial Com-
munications Units mounted to CJ2H CPU Units with unit version 1.1 or later. These instructions enable
high-speed data communications.
• 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
RXDU(255),
DTXDU(262),
Only Start Code
and
DRXDU(261)
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)