No-Protocol Communications - Omron CP1H CPU Operation Manual

Serial Communications
6-1-2

No-protocol Communications

Transfer direction
Data transmission
(PLC → External device)
Data reception
(External device → PLC)
340
No-protocol communications enable sending and receiving data using the
TRANSMIT (TXD(236)) and RECEIVE (RXD(235)) instructions without using
a protocol and without data conversion (e.g., no retry processing, data type
conversion, or process branching based on received data). The communica-
tions mode for the serial port must be set for no-protocol communications in
the PLC Setup.
No-protocol communications are used to send data in one direction to or from
standard devices that have an RS-232C or RS-422A/485 port using TXD(236)
or RXD(235).
Sending/receiving data
For example, simple (non-protocol) communications can be used to input data
from a barcode reader or output data to a printer.
The following table lists the no-protocol communication functions supported
by CP1H PLCs.
Method Max.
amount
of data
Execution of 256 bytes
TXD(236) in
the program
Execution of 256 bytes
RXD(235) in
the program
CP1H CPU Unit
TXD(236) or RXD(235)
RS-232C or RS422A/485
Standard device with
serial communications
(e.g., barcode reader)
Frame format
Start code End code
Yes: 00 to FF Yes:
00 to FF or CR+LF
No: None
No: None
(The amount of data to
receive is specified
between 1 and 256 bytes
when no end code is speci-
fied.)
Section 6-1
Other functions
• Send delay time
(delay between
TXD(236) execu-
tion and sending
data from specified
port): 0 to 99,990
ms (unit: 10 ms)
• Controlling RS and
ER signals
Monitoring CS and
DR signals